Not to mention "working 100 hours a week" is very different when you're the boss and set what your output is expected to be. Working 100 hours a week at the top is very different: it's voluntary (meaning he knows he doesn't have to if he doesn't want to, which means he won't feel trapped doing it), a lot of those hours are probably things like meetings or reading emails or whatever (not suggesting it isn't important, but it isn't the same as doing more involved engineering work for 100 hours a week by any stretch), etc.

And that's assuming we even believe Musk actually genuinely works 100 hours a week. I am sure he is around his businesses and stuff for that time, but I wouldn't be surprised if he took long breaks between doing anything of real value regularly which massively dropped it