I'm not being hyperbolic when I say I believe the explanation is that Musk is a fascist. Fascism is notoriously difficult to define, but what I mean here is that Musk ultimately believes only in the will to power; all stated principles will ultimately be abandoned at the time when they conflict with his will to gain & maintain power. You can compare this to Trump; Trump excoriated Clinton over her handling of classified information wrt her email server, but not only did many Trump administration officials (including his children) make similar mistakes, but we've seen with the document scandal that he had no regard for classified information when it suited him to keep them in an unlocked closet space. (This is not to defend Clinton; I have no interest in doing so.)

So Musk talked about being a free speech absolutist, until such a time as he felt threatened by it. The only thing Musk actually believes is that he is the most deserving person to wield power, and because he the most deserving, anything he does in support of that is justified. He can justify it by saying, I'm making humanity an interplanetary species, and in doing so I will save billions of lives.

(He won't make us an interplanetary species, his plans for colonizing Mars are gibberish, nothing he does is truly justified.)