Anecdotally, if you know a lot of people who act like them. I know very few that are that driven in the face of no further material wants. Not everything needs to be proven. You need to have a bit of a lust for power to want to push to those levels.
The ability to kill all your other competitors does imply something about your intrinsic properties. But I don't think that's very apt in this case, Musk and Bezos aren't intentionally killing lots of competitors in the cradle. The ecosystem comparison might be a bit more apt, and there are certainly a number of people who are very driven and long-term-focused who never achieve the same heights, because you can only have so many megacorps in each field. But I think those people that don't achieve the peak still end up much better off financially than pure luck and circumstance would imply.
I was mainly arguing against the sad-sack sour grapes tendency I've noticed recently to say that very rich people are just luckier, and are no more deserving of their status than anyone else. That is, frankly, bullshit, unless it's inherited.
That's not to say we shouldn't strive to give the educational and financial resources for everyone the opportunity to thrive, I certainly think we should do more there. Bolstering our state university system so that it once again offers everyone the chance for a very cheap high quality education would be a great start.