He could, but then the board could be replaced and the shareholders could fire the CEO.
90% or so of the voting stock would need to agree on a motion to remove him. That's a very high bar to reach and some activist shareholders have petitioned the board to remove those rules. Musk hasn't had a majority in Tesla for a long time now.
Maybe with his latest antics such a majority could be found and then his goose is cooked, at least, as far as Tesla is concerned. Shareholders are probably afraid that the stock would really crater if that were to happen (which, compared to where it is today would open the company up to - ironically - a hostile takeover).
