I would imagine they can find a perfectly good CEO with something like a 500k/yr salary

Look, I understand you can't get a high school dropout to do this job, but can they really justify earning 10000x more than other people in their companies? Are they 10000x more valuable??

Everyone here is talking past each other. There's one crowd raging that CEOs do literally nothing, which is objectively untrue. When that is pointed out, people assume it to be an argument that these CEOs should be paid that much, which it's not.

CEOs do things. If they're non-shit, they'll work significantly more hours than normal workers. No, that does absolutely not justify paying them magnitudes more. Their salaries are inflated, because publicly traded companies pay them that much.
Because while the effort a CEO puts in does not match the salary, the impact of their work does so more closely. As in, if they're doing a bad job, the losses for the company will far exceed that salary.
More importantly, though, you want to keep one CEO for as long as possible. Even if their strategies are mediocre, constantly changing CEOs and therefore flipflopping between strategies is worse.