SAN FRANCISCO — About a month after Donald J. Trump was elected president in 2016, Larry Page, the Google co-founder, was summoned along with other prominent tech executives to a meeting at Trump Tower.
It was a rare public appearance for Mr. Page. He sported a tan suit and shifted in his seat as he introduced himself and noted (incorrectly) that his company was probably the youngest in the room. “Really glad to be here,” said Mr. Page, who did not look glad to be there.
By the time he was again summoned in 2018 — this time to testify to Congress on tech’s various problems — Mr. Page had all but abandoned the roles typically associated with leading one of the world’s richest and most powerful companies. He didn’t show, and senators placed an empty chair and his placard alongside the other speakers.
On Tuesday, Mr. Page and Sergey Brin, his Google co-founder, said they were stepping down from day-to-day executive roles at Alphabet, Google’s parent company. While the move seemed sudden, it was the culmination of a yearslong separation between two of Silicon Valley’s most prominent founders and the company they began 21 years ago.
For some time, Mr. Page and Mr. Brin have drawn down their daily involvement in the company, ceding managerial tasks to deputies so they could focus on a variety of projects, including self-driving cars, robotics and life-extension technology. They left the often messy business of running Google itself to Sundar Pichai, a trusted deputy who became Google’s chief executive in 2015.
Tuesday was the capstone of that split. The founders named Mr. Pichai as the chief of both Google and Alphabet, while they will remain on Alphabet’s board of directors. Mr. Page and Mr. Brin still hold 51 percent of Alphabet’s voting shares, giving them effective control over the company — and Mr. Pichai, if they wish.
In a letter announcing the change, Mr. Page and Mr. Brin compared their 21 years at Google to raising a child, saying now was the “time to assume the role of proud parents.”
Mr. Page and Mr. Brin helped unleash the modern internet and Silicon Valley as cultural and business phenomena. Over the past two decades, they oversaw a company that was central to one of the most consequential periods in the history of business.
Now, as society and government begin to reckon with the fallout of changes wrought by the internet, the two men are walking away, most likely to pursue other projects, funded by the billions of dollars they made at Google and driven by a belief that technology can solve the planet’s problems.
Google faces legal and regulatory challenges on several continents. It is fighting with its own employees. And it is trying to reverse sinking public opinion of its brand. But Mr. Pichai, not the founders, will be tasked with leading Google through the most difficult period in its history.
“It’s an impossible job now,” said Shane Greenstein, a professor at Harvard Business School who has studied Google and its founders. Mr. Page and Mr. Brin are cerebral, technical thinkers, and the issues facing the company “are not merely technical problems or scientific problems,” he said. The problems “are very much corporate lawyerly types of policy issues, for which historically they have not been enthusiastic.”
Mr. Page and Mr. Brin met as graduate students at Stanford University, and in 1996, they came up with a better way of ranking internet search results. It was, at the time, a school project. After they developed their internet search engine, they tried to sell it, but couldn’t find any takers. So they started a company.
That singular innovation gave rise to a company and product that functions as an effective tax on the internet. Billions of people navigate the web through Google’s search box, and it charges a toll in the form of tracked and targeted advertising.
Google has grown to be dominant in several markets. Its search engine handles nine out of 10 internet searches and the company’s Android software powers roughly three-quarters of the world’s smartphones. And for a generation of young people, YouTube, which Google acquired in 2006, has all but supplanted television.
But to some observers, the more powerful Google became, the less interested its founders appeared to be in running it.
“They’re accidental entrepreneurs,” Mr. Greenstein said. “Given their origins, it’s not surprising. They probably still harbor a desire to be a professor with a lab.”
After Mr. Page and Mr. Brin formally founded Google in September 1998, they turned out to be skilled businessmen. Still, investors worried they were not ready to run what many rightly believed could become one of Silicon Valley’s biggest companies.
By 2001, Google’s board pushed the founders to bring on an experienced executive to lead the company. Mr. Page and Mr. Brin picked Eric Schmidt, the former chief executive of the software company Novell, as Google’s new C.E.O., in part because the three had bonded at Burning Man, the arts festival in the Nevada desert.
While the founders were initially wary of having a boss, they quickly warmed to Mr. Schmidt. One of the benefits of no longer being C.E.O., colleagues told Mr. Page, was that he would no longer have to perform tasks like talking to advertisers and investors, according to “In the Plex,” a book about Google’s beginnings by Steve Levy.
Instead, the founders sought out new efforts, such as mapping the world, digitizing books, developing artificial intelligence and creating new smartphone software to rival Apple’s iPhone.
In 2005, Mr. Page attended the Darpa Grand Challenge, a race for self-driving cars in the California desert. There he met Sebastian Thrun, a Stanford professor and leading developer of autonomous vehicles, which were then in their infancy.
“I was flabbergasted that a founder of a search engine company would attend a robot race,” Mr. Thrun said in an interview on Tuesday. “It wasn’t long before Larry pushed me to start the Chauffeur team.”
Chauffeur was Google’s secret self-driving car project, which Mr. Thrun began in 2009 under close coordination with Mr. Page and Mr. Brin. Today, a number of big tech companies are experimenting in transportation, but when news of the project broke in 2010, it was unprecedented for an internet company to be building a car.
“I didn’t think of Google as a transportation company,” Mr. Thrun said. “But Larry thought of Google as a company that pushed innovation in any area.”
Mr. Thrun led Chauffeur under Google X, the so-called moonshot lab where engineers were encouraged to build science-fiction projects they thought might never work. Many of their projects did fail, like space elevators, jet packs and teleportation, but others are still in development, like delivery drones, energy-producing kites and internet-beaming balloons.
Like most of the futuristic projects at Google, the lab was the brainchild of the founders. Mr. Brin particularly wanted something to work on because he was getting bored in management, said Michael Jones, the co-founder of Google Earth who spent 11 years at the company.
“He was always frustrated in what to do; you can’t engineer from the top,” Mr. Jones said. “He wanted to go build things.”
Mr. Brin moved his desk to Google X and began experimenting with computer-embedded glasses, delivery drones and barges in San Francisco Bay that could possibly house data centers.
In 2011, Mr. Page retook the C.E.O. job atop Google, getting something of a hero’s welcome. Yet the pattern — wanting to be in charge, but not wanting to deal with the day-to-day job — would quickly repeat itself.
He seemed no more interested in the menial aspects of the job. He was frustrated by having to deal with things like executive infighting and turf wars that are an unavoidable part of corporate life, according to three former executives who spoke on the condition of anonymity.
Even then, well before the recent employee uprisings, he had grown disillusioned with what he saw as entitled behavior from Google engineers, said two other executives who also spoke on the condition of anonymity. He also started to experience health problems, most notably paralysis of his vocal cords. Executives who met with Mr. Page, who spoke on the condition of anonymity, said he sometimes used an electronic speaker to amplify his strained voice.
“Larry is like a professor who’s a business star. I don’t think he has any appreciation or love or desire to run a company actually,” said Mr. Jones, the former Google executive. “The thing he cares about is pushing toward innovation.”
In 2013, when stock analysts asked Mr. Page about how much money the company was spending on far-off research projects that might never generate revenue, he chided them for short-term thinking and said they should be asking him to spend more. It was the last earnings call for Mr. Page.
“I know you would all love to have me on, but you’re also depending on me to ruthlessly prioritize my time for the benefit of the business,” he told analysts.
Mr. Page did have time for side projects. For years, Mr. Page and Mr. Thrun had been discussing a new kind of vehicle: electric personal aircraft. But rather than try to build one at Google, they pursued a project independently, funded by Mr. Page’s personal wealth.
“We felt flying was too far out for Google and for their shareholders,” Mr. Thrun said.
Mr. Thrun now runs Kitty Hawk, which makes three kinds of electric aircraft. Mr. Page is the primary funder, and he has been visiting a few times a month, Mr. Thrun said. (Mr. Page has had three flying-car start-ups.)
Mr. Page has also invested in an asteroid-mining company. Mr. Brin bankrolled space-travel and synthetic-beef companies. Both helped fund Tesla. And Mr. Brin is building an airship in a hangar near Google’s headquarters.
Some Google employees say the founders have been ceding the spotlight to other executives for years. At a Fortune conference in 2015, in one of Mr. Page’s last public interviews, he was asked about Google’s interest in China, a country the company had mostly exited years earlier.
“I’ve also delegated this question to Sundar,” Mr. Page responded. “I help him think about it. But I don’t have to answer this question now.” He smiled, and the crowd laughed.