If Manafort worked on the Hillary Clinton campaign he never would have been prosecuted
When you are talking about wealthy well-connected men you should include those who worked for Hillary Clinton and did some of the same things Manafort did and were never prosecuted. The main reason Manafort was prosecuted is because Mueller and his team of angry Democrats were trying to extort testimony from him to attack the President. The extortion attempt is likely the reason Manafort got the lower sentence. He may not fare as well in the other case he was tried for because that judge seems more amenable to Mueller's political prosecutions. Paul Manafort’s case was perceived as a high-profile instance of the system working one way for a wealthy, well-connected man, while working in a harsher way for indigent defendants facing lesser crimes.