The National Nuclear Security Administration doesn't oversee the use of nuclear weapons; they maintain the stockpile, do nuclear research, and respond to nuclear incidents.

So ugly thought here:

What if they're trying to maneuver it so that nuclear materials get "stolen."

And the head he just fired was standing in the way of their plans. They're installing a lackey in the NNSA who will do the bidding of the Trump administration, the same way DeJoy did their bidding ... only with potentially far more catastrophic consequences.

If a pit fell into the wrong hands, IIRC, a simple Hiroshima size nuclear bomb can be constructed in a well-equipped machine shop.

What could they do with a nuke or two? The mind boggles.

These people are evil, and don't underestimate their willingness to do the unthinkable.