The risk of exposure in forging evidence as part of a vast conspiracy against the president of the united states (their lives and careers would be utterly ruined, their reputations tarnished for all time, and their families would have to live in shame and disgrace) doesn’t come close to being worth whatever reward you could conjure up for them to be chasing (a long-shot snowball’s chance in hell of impeaching Trump based on forged evidence…are you insane?)
Your position is irrational. The more likely and far more plausible argument is that the investigation uncovered incontrovertible evidence that Cohen is a criminal scumbag, and the conservatives and Trump supporters involved felt morally and legally obligated to followup on that strong evidence in a responsible and professional manner.
As for all the attorney-client privilege arguments. Spare me. I’m as hardcore about civil liberties as they come, but attorney-client doesn’t give someone immunity from criminal prosecution or investigation. As long as the collected information is handled legally and professionally, it’s fair game.