i think mueller has already progressed to such a level, and amassed so much information, that anyone who comes in and tries to stop it would be inviting an obstruction investigation against themselves.

mueller has been clever and successful at keeping his investigation going despite donnie's many efforts to stop it, i have to think he's figured out some ways to protect himself against a corrupt a.g. coming in and trying to shut him down.

and Barr suggests Individual 1 or Pence pardon all of them

though it's one of the few things that donnie can probably figure out without barr or anyone else suggesting it to him.
in fact, i'm sure he's already explored that and had others talk him out of it, for now at least....

Barr is the one who talked Bush into pardoning everyone involved with Iran Contra on his last night in office.