I don’t know the answer but I do know that Trump is much more valuable to The Democrats and their media allies as the troll under the bridge who could come back at any minute to eat us up. An impeachment that had resulted in his “removal” would have defanged the beast and left the Democrats nothing on which to fundraise.
Did they tank? I dunno, but I bet a lot of them are happy they’ll still have Donald J Trump to kick around for a while longer.