It depends. Musk has a great ability of burning his employees out to make up for mistakes he has made: (Early automation efforts at Tesla in 2017/2018 where they repeated the mistakes GM made in the 70s/80s, dumb mistakes in the early days of SpaceX when they tried to replicate what NASA had in the 50s/60s).

In the end he succeeds powering through all the dumb decisions he makes and manages to pull ahead:(Tesla production and engineering is now seen as a innovation leader in the industry and not just dismissed as some dumb flash in the pan, SpaceX has no real competitors, maybe the Chinese will eventually catch them but no one else is even in the conversation).

I have often wondered why so many people sign up to put themselves though this and I guess the clearest answer I got was when I interviewed some Starlink employees at DEFCON. They just want to be part of a team of excellent players and will overlook Musk's faults to be a part of that team.

In Walter Isaacson’s biography of Musk, one of his employees completely burnt out and quit. Then came back years later because he was bored and wanted to be part of something cutting edge again.

Yeah I remember that. Honestly I wish there was some other organization that could rival the Musk companies. We need to spread out the power that he has right now but man I just don't know what the other guys are doing. Just today I saw the Rivian and Lucid financial results and they are not looking good. On the space side I'll take Bezo's Blue Origin but I hear almost nothing good.

How horrible mismanaged have all other big companies have to be, for someone like Elon Musk to easily overpower and overtake them?

It's not like overworking employees is a novel concept no other big corp has left untried.

I think attributing Musks success to "overworking employees" is either completely wrong or not sufficient to explain his success.

You can't say it's by chance, because it's not his first and last successful company either.