A critical aspect to understand is that Clinton, Comey, Lynch, Brennan, Baker (FBI general counsel), Powers and Rice could all wind up in prison for actual felonies committed. They bet the farm on Hillary's election, and continuing coverup of their crimes, while they held the reins of power. With Trump as POTUS, all bets are off, and they are going for broke with the deep state coup, to save their own necks by taking out Trump before they are taken out.
Opinions on that position turn on how one views the selection of Mueller, out of all the people in the world, to go after Trump.
I think Rosenstein was more or less forced, by circumstances, to appoint a SC. Sessions was sidelined by reasonable protocol. He can;t be used or seen as using his power to favor Trump or disfavor Hillary. That's good for him, and it's good for the system and it's good for Trump - Sessions is not the only warrior on Trump's side.
Rosenstein, being the source of rationale to fire Comey, and also being a "Trump boy" for being nominated and appointed, has a similar problem as Sessions, just muted.
But the turd that Comey left in the punchbowl, the "open investigations" cited in his March 20 testimony, those have to be publicly closed.
Enter a SC. Maybe Rosenstein thought Mueller was clean, although that isn't a credible belief, Rosenstein can't be that naive. Maybe the selection is done with the expectation Mueller would expose himself, given the opportunity.
At any rate, list out those that ought to be prosecuted and jailed. I don't think Rosenstein is on that list. Clinton, Comey, Lynch, Brennan, Baker, Powers and Rice (and there are more), yes, they are on the "prosecute and jail" list. Mueller could be too, or at least he is in the same cohort having "deep state malfeasance cover-up artist" as a career.