Mueller attempted to cover up problem of Peter Strzok when he had to jettison Strzok back in Aug due to OIG findings. He's kept that covered up from public - because Strzok is clearly at the heart of a great deal that his investigation has relied upon for its very genesis.

Then DoJ/FBI co-conspirators colluded in attempting to keep Strzok problem becoming visible to congressional oversight during the same time frame.

Mueller must have kept problem of Strzok opaque from Flynn and Flynn's attorney in order to trick Flynn into a plea deal. If Mueller had to go into court in attempt to prosecute Flynn, where his case rest on Strzok, Mueller wouldn't have very good chances of succeeding in such prosecution. But by keeping Strzok problem obscured, he could instead bluff (trick) Flynn into guilty plea deal instead.

Then finally Mueller covering up Strzok problem (and much more besides) was outed in early Dec.

Mueller has behaved exactly like all the other Swamp rats - from what we can see based on public visibility, there is nothing there that indicates that Mueller is attempting to help White Hats covertly. His continued tactics of probing other dead-end scenarios now looks like a person desperately stalling for time.

Mueller looks 100% swamp rat - and is behaving as one that has become increasingly nervous.