Geoffrey Berman is a well-respected attorney who was named successor to Preet Bharara as United States Attorney in the Southern District of New York, a jurisdiction also known as the Sovereign District for its fierce independence. Berman calls himself a Rockefeller Republican, and if you know what that is, you are either as old as I am or pretty well-informed. He felt obliged to explain how he came to take a job working for Trump, and like many of Trump's hires, he made the case that he was better than anybody else Trump might choose. He was aware that he had to win over his assistant US attorneys, and was upset when one of his first decisions went against their virtually unanimous advice. He turned out to be right, and that and his open, collaborative style won his employees over in no time.
The cases Berman worked on were major and the pressure from Washington was unrelenting. Berman names the names of people with whom he interacted face to face, but did not speculate as to who was the prime mover behind the scenes. After Sessions was fired, Barr became an even more persistent presence, trying to direct and dictate to the SDNY the cases they would investigate and the ones they would not, to insert more favorable lawyers or officers over Geoff Berman, and eventually, to replace him.
Berman is personable, and his approach was to avoid whatever conflict he could and let the thing play out until he had to make a stand. Then he made his stand, and was most often successful in backing Barr off. Critics say we should have known all the back story at the time, but I think Berman is correct in saying that he couldn't talk about all that and remain a US Attorney. He did a creditable job in his own defense, and I tend to accept that he took a reasonable course. Absent other evidence. Regardless, it was a good look at how it all worked.