Joy Reid, sitting in for Rachel Maddow, had a guest on that made a very useful point. Trump brags about his memory and how smart he is when people criticize his abilities.
On the other hand, when he is asked questions which have legal implications, or would point out his waffling and other dysfunctions, he suddenly is unable to remember anything and does so repeatedly, and will often say, it isn't or wasn't important.
Another guest said that Trump's attempts to fire Mueller is the nail in his coffin. Along with other evidence and testimony, it is now clear that Trump has obstructed the investigation. That is a crime.
(Heckler in the Real Grassroots (UNPAID) Crowd)