It's very easy to avoid investigating the actual Russian collusion when the three principals in charge of and have knowledge of the facts are chosen to embark on an investigation in a 180 degree opposite direction.
Too many residents of the Swamp on both sides of the political aisle don't want a thorough above board investigation of actual collusion to be conducted. It might uncover lots of unsavory details and alliances.
Too bad nobody like... filed charges or something to get it all out in the open.