I could believe that he thinks he's that billionaire. However, his competence leaves something to be desired. Just yesterday, he had a peace proposal for the current Russo-Ukrainian war that boils down to "give Russia everything it wants" on the basis that that's what the eventual peace is going to be, the fact that the Russian military and milblogger sphere is in full-blown panic over Ukrainian successes in Lyman and near Kherson. Or take this case, where Musk and his attorneys have completely shot their credibility with the judge--in a case where there will be no jury, only the judge ruling on the merits.
In short, Musk does seem to have the tech-bro attitude of "I always know what the right answer is, and everyone who tries to tell me otherwise is an idiot." That is not the kind of person I want working towards humanity's best interests.