I will not deny for a second that Zuckerberg dreams of having the kind of big monopolistic platform that would let him single-handedly suppress speech he doesn't like. However, that's still not as bad of a harm as being thrown in jail for the same thing. There's a huge gulf between "large multinational corporation" and "sovereign nation" - the former can still have it's power challenged through antitrust law and regulations, while the latter is immune to such things because they have their own military.