[twawaaay]

I think the mistake is assuming that there is any connection between amount of work put in and your productivity as a CEO.

Even for a developer, various people can be wildly differing in productivity, by order or more of magnitude.

When you become high level manager it is some of your key decisions that will decide how successful you (your company) are.

Those decisions do require preparatory work, but here people can really be on completely different levels. If you do it well, you can get the information fast, ask questions fast, make decisions fast, delegate the work and set up systems to get notified if something isn't working smoothly. Finding trusted people to delegate to is paramount.

It is not like Elon Musk is doing all this job himself. He decides what he wants to do himself, what is important at the moment and what can be delegated. If you are able to find trusted people to delegate stuff to and you can devour knowledge (as Musk is known to be able to do) I think there is not a huge issue in being CEO of multiple companies other than shareholders being a bit concerned that if stuff will blow up he may not be able to put multiple fires at the same time.