I've gotten the impression that a lot of people at high levels get there through a kind of self-perpetuating prestige cycle, often starting at an elite school and jumping between high-prestige jobs from there. The measure of success is not what they've done (which is mostly taking credit for other people's work), but what it looks like they've done. Starting a big-name company matters more than whether that company goes belly-up five years later. The people who end up on top are the ones who get extra-lucky and capitalize on it.
A recent example from tech is Adam Neumann (the WeWork guy) who came up with an absurd business model for commercial real estate, led a widely-ridiculed IPO, and lit a billion dollars of other people's money on fire. A couple years later a16z announces they're giving him a third of a billion dollars to fail again because (paraphrasing from memory) he was the only person who made a profound effort to transform the real estate market.
You can also see smaller-scale examples in media. There are New York Times op ed columnists who have been wrong about everything for decades, but they keep getting invitations from talk shows and universities and publishing companies because of the prestige of being a NYT columnist. But a big reason they're still a columnist is because of all the prestige they get from doing that other stuff.
It's a circular process, and it seems to be hard to fall out of unless you fail publicly and catastrophically. Sometimes it takes multiple such failures. These people all run in the same social circles, which probably also helps. I suspect an awful lot of elites would fare poorly in a real skill-based competition for their official jobs, and consciously or unconsciously act to prevent such a culture from developing.
I don't know any of these people personally, so take this with a large grain of salt. But in the case of Musk, it's clear to me that nobody who spends that much time being a flamboyant asshole on Twitter can be getting any real work done, much less running 2-4 different companies at a time. His real job is prestige development. I'm not sure he has anything in his playbook that doesn't rely on a pre-existing desire to work with The Great Elon Musk and his Great World-Changing Companies. Like many elites, when forced to focus on his official job, he is mediocre at best.