I agree, it's very selective prosecuting.
Perhaps, but Manafort knew he had been under FBI scrutiny. Despite that, he continued to launder money and commit bank fraud. Nobody forced him to do that or contact Kilimnik to provide polling information for who knows what. Most of the people that have come under scrutiny, related to Trump (Manafort, Papadopoulos, Page, Whitaker) have been recommended by Sam Clovis. You have to wonder about him, at some point.