Barr tried to get rid of Berman, head of the SDNY. It backfired on him. But this demands context. For over a hundred years, SDNY is the district that made it's goal to be the best, and completely non-political. It is sometimes called the Mother Court, because it got going a little before the Supreme Court. Few know it outside the law, but SDNY is special. Berman refused to step down, and while Trump fired him, Berman won the negotiation. By law, the replacement is the deputy, in this situation. But neither Barr or Trump has shown respect for the law. If I had to guess, I'd say Berman had a card to play, perhaps something to do with obstruction of justice charges. "It is telling that we do not know which of many possible investigations may have triggered Barr’s ire. There are so many to choose from." https://www.washingtonpost.com/opinions/2020/06/21/friday-night-massacre-that-backfired/ The timing is the key. Just over the last several days, things have been going extremely badly for Trump. In my distinctly unhumble opinion, he wanted a corrupt crony to get in there, and do as much as he could to keep Trump out of jail after he loses. I saw a law professor say that this wouldn't be the end of it.