Well, I think there are some good reasons for that. It's traditionally been an antisemetic trope, and often smoothly blends into antisemitism (Rothschilds, etc). It's also one of those things where the evidence is by necessity weak, and you really can't write weakly-evidenced critical articles about rich people without getting sued.

Personally, I'm very glad that this isn't a mainstream way of understanding problems. Rich people are kind of fungible, in that they usually don't want to pay taxes, but other than that usually have about the same range of politics as everybody else. Focusing on individual malfeasance tends to protect dysfunctional systems.