I know this is tangential to your main point, but in the US, you can only give a max of $3,500 to a candidate per election cycle, for each the primaries and general election.
To give more financial support, you have to do independent, uncoordinated campaigning for the candidate. So you can spend a million dollars on ads saying to vote for a candidate, but you can't give that money to the candidate's campaign and the candidate can't coordinate with you. This is what Super PACs do.
I only write this because a lot of people are unclear on the rules. I'm not making an argument about billionaires.
That’s the law, yes, but in practice it’s murkier: https://www.opensecrets.org/news/2023/08/super-pacs-raise-mi...
> In fact, not a single coordination investigation has ever resulted in a PAC being fined.
As one example see million dollar donations to inaugurations.