X is owned by an opinionated rich guy, completely entangled in government (even before the Trump win.) There's nothing ideal about a situation where he could be flipping the switch right now to turn it back like it once was, or even worse. He doesn't even have to care, all he has to do is lie back and let it happen. It's the path of least resistance.

I firmly believe his posture with twitter has been because 1) it's a fun place for him and it was obviously a money losing purchase* so he might as well have that fun, and 2) his level of censorship is something that he can use to negotiate with government over contracts or regulation.

He might even really believe in free speech, but a conceptual belief in free speech doesn't mean he'll feel obligated to personally provide it if he can make a dollar denying it. His speech will remain free no matter what happens, he's a rich guy.

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* (not unlike say the Guardian, the New Republic, Mother Jones, the Intercept, or the Atlantic, or the WaPo, aparently, and probably CNN and MSNBC at this point. They're not for making money.)