Less true for art museums and things because wealthy people can get more out of their donations, like their name on stuff and cool party invitations.
that's an easily-testable hypothesis. I dispute it.
As for "Wealthy people are too rare to matter" do a search on the percentage of income taxes paid by the wealthy.
Less true for art museums and things because wealthy people can get more out of their donations, like their name on stuff and cool party invitations.