Not to quibble but he was appointed by Sessions as interim US attorney, and then after no action was taken to make the appointement permanent by Trump, the judges used their power to do so for an indeterminate time “until the vacancy is filled”.
It’s a moot point now in any case, but you have to wonder what was going on. Did Trump not like Sessions choice? I forget stuff all the time but I don’t think Trump would just forget about the SDNY US attorney. If it was intentional to allow the judges to do so, I can’t see why because once they did so he had all the powers of the office, unless as you suggest he was being used somehow.
A final spitball: Suppose the Clintons were a part of his removal. I’m going to guess the DOJ has known where Maxwell has been hiding since before June 20. Maybe Berman was dragging his feet on Maxwell because it would lead to the Clintons? Maxwell being arrested 12 days after he was removed cannot be a coincidence.
We may find out someday - or maybe future actions by the acting and new US attorneys will provide some clues.
Thanks for the corrections about Berman being appointed interim by Sessions. Whatever the reason/s, I am sure Trump and his people kept Berman there on purpose. Mabye he would have told targets what was going on, for another possible reason to keep him in place for a while, as well as my other possible reasons.