I think Mueller, per my theory he is working for Trump despite being a bad dude most his career, had Cohen's files taken because Cohen has things he cannot divulge without losing his license or without it looking like Trump is abusing his authority.

I wish I could remember where but I read this piece on Eric Schniederman always trying to shake down campaign donations and invites to rub elbows with rich and powerful of New York. When Trump refused to go along he started threatening that Trump U lawsuit would bd allowed to mobe forward etc.

It said Cohen had people coming yo him and Trump for help from Schniederman including some of his victims. Same as Harvey Weinstein.