....... My Guess is that somebody of note in Mueller’s text thread was fingered in the so called “4 Page Memo” which probably contained damning evidence of treasonous actions and therefore those threads have magically vanished into the netherworld of Unamerican Activities which seems to be so fashionable these days. In Short ..... No evidence .... No prosecution. And the Happy Traitor gets to keep that smarmy smirk on his or her face.
I have faith that there are truly Patriotic Americans still working within these organizations. They are merely waiting for Sessions or Trump to remove Mueller and escort his team from their premises.
Once the overt threat is removed, they may whistle blow.