What is Musk really doing with his $43 billion offer to buy Twitter?

Mercurial billionaire Elon Musk now says he wants to buy Twitter outright, taking it private to restore its commitment to what he terms "free speech." But his $43 billion offer, which fell flat with investors and raised the board's hackles, bring up as many questions as it answers.

Among them: Is he serious? Can he get the money together? Would a sale make shareholders happy? And what would the social platform look like if he succeeds?

Twitter said its board "will carefully review the proposal." But one major investor has already come out against the offer. Saudi Arabia's Prince Alwaleed bin Talal, who Bloomberg News reports controls more than 4% of Twitter, said on Thursday that "I reject" the offer.