If you had 100 dollars would you invest it into a company where the CEO could just take the entire company hostage and potentially make you lose your entire investment?
It's pretty much like that already, the CEO can run the company into the ground for funsies if they are insane.
But if the investor catches the CEO doing this they have the right to sue to prevent it from happening and the legal system and shareholder primacy are what allow for this. Otherwise, what does the concept of ownership even mean if the owner can't decide what is done with the business?
Company actions will maximize company value. Employee actions will maximize employee value. Customer actions will maximize customer value.
That's a false dichotomy. You can own something (or a share) and the purpose of it need not be "return as much value as possible, via buybacks, in the next quarter".
FWIW that's just logic.
Whether it's de jure or de facto, the owners of something will own it to their interests.