I have no deeper understanding about Putin's inner cycle. According a detailed news article yesterday there are only 2 oligarchs left there. He prefers people with way less money these days because they are easier to control.

Most oligarchs are completely silent on politics, some are even in prison for corruption. Which of course is not difficult to accuse anybody rich or powerful in Russia. They probably don't have to dream up the evidence like in other cases of political (in)justice.