I think impeaching allows Trump to control the agenda "look at all these do nothing Dems spending their time trying to stop me make America great again". We all know he's guilty and we all know the senate won't convict him. The Dems are better of passing legislation that will improve people's lives and leaving Trump with the decision to veto it or not. At least they can set out an agenda of what they could achieve if they had a trifecta.