My dad was a gunner on Liberators WWII and made the Air Force a career of it, I grew up on SAC bases, my brother was career Air Force also, so it holds some interest for me.
I think there are a few things the Pentagon won't say are at work here. One it was a message to nuclear nations that are possible adversaries. Another would be a quiet calculation that several nations in the ME will join the nuclear club, a new paradigm. Another is the recent embarrassing failures and incidents involving the Air Forces Nuclear Forces.
There are also practical maintenance and organizational matters that one would have given for not (for lack of a better word disbanding) SAC.