CEO is a hard role not because of domain area but because of risk and uncertainty, both of which tend to be low when you're "at the bottom of the food chain."
Maybe this site should add a CEO skill map!
In my engineering school, mechanical engineers were taught the basics of electrical engineering.
There is a lot of value in gaining a good amount of breadth before specialising, even if just to ease communication with specialists of adjacent fields.
Lionel Messi doesn't try to be the best header or best defensive midfielder. He focuses on dribbling and scoring goals.
In the latter, he also touched some GTK code: https://github.com/torvalds/subsurface-for-dirk/commit/c0adf...
Trovalds has much more breadth than you give him credit for.
I do think he's in the top 5% of MDs, so of course we can't expect this of everyone. And specialists obviously specialize. But there is a large segment of the profession that requires a wide breadth of knowledge in a domain that frequently changes.
BTW, my career has been focused on development, but I still try to maintain enough knowledge that I could jump in at any point of the stack and be useful.