I tend to believe that Mueller is not a black hat. He is posing as one for the benefit of the swamp. He may be a forced gray hat. I think he’s gathering evidence, especially via Lt Gen Michael Flynn. Like Q says, Flynn knows where the bodies are buried.
Here are some twitter posts I found interesting;
https://twitter.com/GodandCountry11/status/1133754412244058113
https://twitter.com/LisaMei62/status/1134630739918708738
Clandestine wrote;
Does it make sense as to why Flynn caught the minor process charge? Flynn WANTED to give his testimony. Flynn knows where the bodies are buried and he told Mueller all about them in his 19 interviews. any and all crimes with which you are familiar. Legal injection.
https://twitter.com/RodSneaky/status/1134835708357697537
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I know it, right?
Mueller was ultimately beneficial for POTUS, and appears to be playing a role in a play (a tragedy, of course).
Yet, somehow, his (and Rosenstein's) decision to totally ignore all the RAT wrong-doing will need to be explained ... at least for the benefit of history.