Isaacson, who shadowed Musk and interviewed him for two years to gather material for the book, claimed that in December 2016, the entrepreneur held a private meeting with Trump to see if was capable of leading the country.
The author claimed Musk was "baffled" by Trump's comments about brands like Tesla and NASA.
"He seems kind of nuts, but he may turn out OK," Musk said of the former commander-in-chief after their gathering.
After Joe Biden took over the Oval Office, the tech guru still held a "deep disdain" for Trump, "whom he considered a con man," the writer spilled.
That's one of the reasons Musk originally agreed Trump needed to be removed from Twitter. "I want to avoid the b------- disputes about Trump," he said. "If he’s engaged in criminal activity — it seems increasingly that he has — that’s not okay. It’s not free speech to subvert democracy."
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Trump's Twitter ban is why he launched his own platform Truth Social — though in November 2022, Musk allowed him to return.
Still, he insisted to Isaacson, "I’m not Trump’s fan. He’s disruptive. He’s the world’s champion of b-------."
Elsewhere in the tome, the author shaded the SpaceX founder, confessing, "He has so many personalities, almost like multiple personalities and a bit like his father."
Isaacson said Musk's dad "is a Jekyll and Hyde and sometimes goes very dark" and that sometimes "happened to Elon, too."
Mediaite obtained the excerpt of Isaacson's biography.