Bill Gates, left, and Elon Musk. (GeekWire File Photos)

Walter Isaacson’s new book “Elon Musk” reveals more details about the billionaire beef between the Tesla chief and Microsoft co-founder Bill Gates.

In an excerpt from Isaacson’s bio on CNBC, the author writes about a March 2022 meeting between Musk and Gates at Tesla’s gigafactory in Austin. The plan was for Gates to pitch Musk on philanthropy and worthwhile projects he could be backing.

But things turned sour in a hurry when the subject of Gates shorting Tesla stock came up. Isaacson wrote that Gates had placed a big bet that Tesla stock would drop in value, and when he turned out to be wrong, he had lost about $1.5 billion by the time of their meeting.

Gates reportedly apologized to Musk, but it didn’t help.

“Once he heard I’d shorted the stock, he was super mean to me,” Gates said. “But he’s super mean to so many people, so you can’t take it too personally.”

When the two reconnected via text the following month, Gates tried to restart the philanthropy discussion. But Musk wasn’t letting go of his anger over the stock shorting.

And he didn’t hold back in his assessment of Gates in a message to Isaacson.

“At this point, I am convinced that he is categorically insane (and an a–hole to the core),” Musk texted Isaacson right after his exchange with Gates. “I did actually want to like him (sigh).”

In a post on X on Monday, Musk lobbed more criticism at Gates over his short position on Tesla.

“The lack of self-awareness and hypocrisy of Gates who had the nerve to ask me to donate to his mostly window-dressing environmental causes, while simultaneously aiming to make $500M from Tesla’s demise, boggles the mind …”

Musk and Gates have bumped billionaire heads a number of times. In September 2020, Musk said Gates “has no clue” when it comes to the viability of electric trucks, and he previously ripped Gates for his purchase of a Porsche Taycan as his first electric vehicle.

“My conversations with Gates have been underwhelming [to be honest],” Musk said via X — when it was still Twitter and he didn’t own the social media company.

The criticism goes both ways, thanks to Musk’s controversial opinions on the coronavirus pandemic. Gates told CNBC that while Musk makes a “great electric car” and his “rockets work well,” a “high level of outrageous comments” are part of the Tesla CEO’s positioning.

The criticism is not limited to Gates.

Musk has lobbed insults at other tech big shots, including Meta CEO Mark Zuckerberg. whom he traded barbs with in 2017 artificial intelligence. He called Zuckerberg’s knowledge on the concept “limited.”

And Musk has also tangled with Amazon founder Jeff Bezos over the company’s acquisition of self-driving vehicle company Zoox and over various aspects of the two billionaires’ space race.

Like what you're reading? Subscribe to GeekWire's free newsletters to catch every headline

Job Listings on GeekWork

Find more jobs on GeekWork. Employers, post a job here.