I like Dershowitz, however, no one knows what Robert Mueller did or is doing because he is investigating, not going on news shows to tell what he is doing. Everyone has an opinion and it means nothing. When his investigation is over and his report is done, then the public will know and not until then.
I don't second guess this qualified investigator. Praise was heaped on him when he was chosen. Now, he is the crazed investigator needing to be fired. I knew this would happen when it started. Think back to the Nixon investigation and the Clinton investigation. Those investigators got the same treatment.
The latest right this minute on the news, Trump expects a letter of exoneration from Mueller.