As he was shaping Amazon into one of the world’s most valuable companies, Mr. Bezos developed a reputation as a brilliant but mysterious and coldblooded corporate titan. He preferred to hunker down in Amazon’s hometown, Seattle, at least partly because he thought it was better for Amazon’s growing business, largely avoiding public causes and the black-tie circuit.

But while Mr. Bezos — who at 54 is the world’s richest person, with a net worth of more than $100 billion — can afford virtually any luxury, obscurity is no longer among them.

Amazon, now a behemoth valued at more than $600 billion, has become one of the faces of “big tech,” along with Apple, Alphabet’s Google and Facebook. These companies are facing a backlash. Amazon is under the microscope for what critics say is its corrosive effect on jobs and competition, and Mr. Bezos has become a bête noire for President Trump, who repeatedly singles out him and Amazon for scorn on Twitter.

“People are starting to get scared of Amazon,” said Steve Case, a co-founder of America Online, who recently started an investment fund focused on start-ups in underserved areas, with Mr. Bezos among its contributors. “If Jeff continues to hang out in Seattle, he’s going to get a lot more incoming. Even for just defense reasons, he has to now play offense.”