On March 13, 1986, Microsoft became a public company. Its founder and CEO, a 36-year-old Bill Gates, took a seat on its board of directors. Thirty-four years later—exactly to the day—Gates is stepping down.

Gates explained the move on Friday in a brief LinkedIn post, in which he also said he was leaving the board of Berkshire Hathaway, the conglomerate led by his longtime friend Warren Buffett. The reason for these departures, Gates wrote, was “to dedicate more time to philanthropic priorities including global health and development, education, and my increasing engagement in tackling climate change.” Coming as Gates joined the epic battle against Covid-19, the timing seems particularly apt.

Microsoft has been thriving under the leadership of CEO Satya Nadella—it is now a trillion-dollar company, reaching a market value that it never approached under Gates. But the founder’s absence from the board leaves Microsoft ever so slightly altered, and almost certainly deprived. Despite leaving his full-time position at the company in 2008, Gates has continued to devote attention and passion to the giant he founded, and no one serving as a director could possibly bring the gravitas and pedigree he carries to the boardroom. (He still holds 1.3 percent of the company’s shares, valued at about $16 billion.)

This current move appears to be the culmination of a 20-year process of Gates’ attention shifting to philanthropy. In 2000, I was summoned to Microsoft, ostensibly to join several reporters for a debrief of the company’s product vision. Instead we were ushered into a television studio for the surprise announcement that Gates was yielding the CEO post to his longtime lieutenant Steve Ballmer. (He still held the post of executive chair and created a role for himself as chief software architect. At that time, he was just beginning to ramp up his philanthropy through the Bill and Melinda Gates Foundation, which evolved from earlier charitable efforts, and pledging to give the bulk of his fortune to the organization. (Since Gates was the world’s richest man at the time, that fortune was considerable.)

Eight years later, Gates left his full-time post at Microsoft to spend most of his time with the foundation. This time, he announced the move some months in advance. When I interviewed him on the eve of the change, he conceded that it would be a tough separation, but it was clear he had found philanthropy satisfying, approaching it with the same enthusiasm and geeky problem-solving that he devoted to software. Six years ago, he inched yet further away from the company that once defined him. He resigned as Microsoft’s board chair, while maintaining a board seat.

Over the past few decades, the image of Gates as a hubristic bully during the losing antitrust fight Microsoft waged in the 1990s has dimmed. He’s also a happier warrior. Though taking on polio, poverty, and the rising of the seas might seem more stressful than fighting Steve Jobs, Sony, or the Justice Department’s hired legal gunslinger, David Boies, Gates has approached the challenges with a humor and humility you seldom saw when he was speaking for Microsoft.

He still lights up when he speaks about his role at Microsoft as adviser and mentor, one that he said in his LinkedIn post that he will continue. But he is turning 65 later this year, an age when normal people traditionally think about retirement. That's not really Gates' path. As viewers of the Netflix documentary “Bill’s Brain” saw last year, he engages in problems of world health—from saving the environment to building a waterless toilet—with the verve that he once devoted to slaying Lotus and Netscape.

When Gates left his software architect job at Microsoft in 2008, he told me that the subjects he tackled at the foundation were more vital than the ones he made about software. He mentioned one decision in particular: He had to choose between two kinds of malaria vaccines to support. “One of those paths saves millions of lives, compared to the other path,” he told me. “I've never had a Microsoft decision that had exactly that character.”

Now he’ll have even fewer Microsoft decisions. Bill’s brain has other work to do.

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