This is not a problem if "Democracy" but of "American democracy". You dont have to accept donations. You dont have to allow bribery. Democracy is wonderfully flexible, and a law that anybody seen attempting bribery of an official (defined however you want to define that) is instantly ousted, and unable to be an executive officer at any company for a period of however many years, is completely compatible with democracy.

Good democracies are built around making it take only a single good person for a good outcome, whole requiring vast conspiracies to get a bad outcome. American democracy has failed by making it nearly impossible to do anything good, while providing the bad actors near universal access to do as they please.

I don't like Trump, but the very idea that Elon Musk should, by virtue of being the richest guy, have any leverage against him, chills me to my last democratic molecule.