I can deny that his enthusiasm and single-mindedness are the reasons for his success.

His initial success, PayPal, was just a matter of being in the right place at the right time. Online payments are an obvious thing and a natural monopoly. He guessed right that PayPal would be the one that succeeded.

That gave him the opportunity to place more big bets that paid off. Neither electric cars nor reusable spacecraft were obvious wins the way online payments were, but it's also no sign of genius to have happened to place bets on companies that succeeded.

The evidence for that is that his luck ran out. He keeps backing audacious projects, and they keep failing. Anybody else would have been bankrupted a dozen times over. He keeps going because he got lucky the first time, with so much money that it's almost impossible for him to lose it all.

That is to say, I think it's more survivorship bias than the merits of his "enthusiasm and single-mindedness". A decade ago he had such a string of successes that I would consider the case that he was actually smarter than average, but he's had such a string of conspicuous and obvious catastrophes that the net result simply seems average at best.