They were grounded several years ago for about 3 months for lack of funding.
That was under the sequester, where Obama canceled White House tours, air show funding, and all kinds of other government activities that average citizens actually enjoyed. Purely a punitive move so they could blame Republicans for the loss of those things.
The air show teams are normally well-funded because they are highly visible and impressive ambassadors for some of the things that the US government still does very well.
So were half of all squadrons in the USAF. It was all part of sequestration, not something more sinister.
It was sequester and it applied to every part of the military, not just the BA.