Three possibilities...
1. Mueller was an all too willing co-conspirator acting as a frontman utilizing his reputation to legitimize the coup attempt by Weissman, Rhee, Zebley etc. with little to no direction or oversight.
2. Mueller was a cognitively disabled frontman that simply allowed Weissman etc.to run the entire Trump/Russia probe with little to no oversight because of mental incapacity.
3.Mueller truly was a fully functioning “hands on” administrator of the Trump/Russia probe and directed and oversaw all actions by his team. (least likely)
I give you a possible
#4.
To receive leniency in his complicity in the U1 scandal, Mueller was brought around to be a gray hat and do what POTUS wanted, to drag out the investigation and troll until Trump had all the evidence against the deep state to bring down the House and the FBI and the CIA, etc.
(I think Sessions is a good guy).
4. Mueller was a secret Trump operative. Jeff Sessions really fooled us all and appointed special investigator that he knew Trump knew would come back with a report of no collusion.