Here is my take on Barr
Trump's team could not get Muller stopped, they knew he was going after obstruction, because Trumps team knew they had nothing on collusion.. Muller could go on forever, and was… so they had Barr wright a letter to Rosenstien and explained obstruction in detail. Rosenstein didn't take the bait. Barr didn't want to come back into government or work for Trump. Barr agreed with the Trump lawers so they needed him on board. So maybe he is there to clean things up and then he gets to move to the next Supreme Court Justice. he is of great legal mind, and he is old school and does not think what is going on is good for our Country.