Bill Barr was raised Deep State. Long intelligence. Much of his own Poppy Bush/Iran Contra crime of his own to keep buried. Longtime and continuing pal of Mueller.
Trying to convince people that Barr is anything other than a run-of-the-mill, deep-state, chicken-shit, political puke lawyer will be an uphill battle at the moment. He’s not looking all that good at the moment passing the buck(s) to special prosecutors who’re looking like they’ll take forever to do nothing.
The answer to the question is: I don’t think they had to.