I feel like Luthor was a better counterexample for this before the model for his billionaire redesign was elected President of the USA.
Even so, Luthor hasn't had quite the same volume of appearances as Iron Man, Batman, Captain America and the other rich superhero tropes.
People have grown up reading comic books and watching movies about generous billionaire superhero saviors. They want to believe that exists because it's what they've been taught justice looks like.