Yet Gates, the man who founded the business now worth $2.9 trillion, said Nadella was nearly passed over for the top role. This was despite the fact that the two previous CEOs of the tech giant—Gates himself and his successor, Steve Ballmer—backed Nadella for the job.

Now focused on his philanthropic work, Gates said in an interview this week that it was emotional to hand over the CEO title of the business: “I’ll tear up on this, ’cause it meant a lot to me. I’ve had two successors, and boy, do I feel lucky because as I went off to do the foundation work, the one thing that plagued me was: Was I going to see the company fade in terms of its excellence?

“Would I be haunted by: Should I go back, should I not go back?”

Gates stepped down as CEO of Microsoft in 2000 and was replaced by Steve Ballmer, who had been recruited by Gates in 1980 to be the company’s first business manager.

In 2013 Ballmer retired from the business, with speculation rife about who would take over the leadership of one of the world’s largest businesses.

Speaking to Brad Smith, Microsoft’s vice chair and president, Gates said: “The fact that Steve took us [Microsoft] to new heights and the fact that through a process that almost made the wrong decision—although you and Steve and I never wavered from knowing Satya would be good, and he’s been even better at navigating what even today remains one of the most complex CEO jobs in the world—makes me feel so good that I get to just come in and play a very bit role of doing product reviews, learning about AI, getting some help from Microsoft on the work that I’m doing.

“It’s allowed me to throw everything in and to have the incredible resources that my Microsoft ownership created.”

Gates has long lauded Nadella’s friendship and leadership, telling the Wall Street Journal previously that in some respects his successor is a better leader.

In 2017 Gates told the Journal: “I’ve come to value empathy more over the course of my career. Early on we were speed nuts, staying all night [at the office, thinking], ‘Oh, you’re five percent slower as a programmer? You don’t belong here.’ It was very hard-core.

“I think as this industry has matured, so has what’s expected of a CEO. Satya has a natural ability to work well with lots of people, to tell people they’re wrong in a nice way and to let feedback come through to him more than I did.”

Fortune reached out to Microsoft for comment but has had no response.

Leading with humor

Smith and Gates also reflected on their work together in the early 2000s, when the C-suite at Microsoft was pulled in front of an antitrust trial alleging web browser dominance.

While Gates admitted his sense of humor was perhaps not best suited for a deposition, he added it has been an important aspect of his leadership.

“I’m not trying to get anyone to feel sorry for me, my life is not one anybody [should] feel sorry for,” Gates reflected. “But I think there are some lessons out of how we went through what felt to me like it could have killed the company altogether…and so through that intensity, you’ve gotta have a sense of humor.

“There was that time when I was testifying and during the break the clerk comes up to me and says ‘Mr. Gates, I know people who have your scholarship, and what are you doing in D.C.?’ And all my complex testimony that day, the press covered that guy coming up to me and it made me seem at least a tiny bit more human than my image at the time was.”