My theory is that Nunes has found out some of what fennstein and grasslet were told in their secret bunker FBI briefing (the one where they came out looking utterly bereft and shocked)
There's some seriously damaging stuff on Nunes. And others. But in his actions, Nunes is throwing the dead cat to distract from Manafort et al.
It won't work. This juggernaut may well be unstoppable now.