This entire thread is basically TMC members guessing about Elon's motivations. Hell, 25% of this site is.
The details maybe, but not the overall arching goals. I mean, yes, what exactly does "free speech Twitter" mean? I would bet you that Elon himself doesn't know the answer to that question. But there should be little doubt that his overall goal is improving Twitter as a useful platform through various changes (like subscriptions, identification and editing) and increasing the ability for people to speak on topics. What he isn't trying to do is a lark, sticking it to the SEC, make money, or increase his own ability to say things on Twitter, all of which supposedly smart people have suggested.