I assume the "almost everything" is relative to the things people need to calculate gravity for. Astrophysics is cool, but rather the minority compared to, say, calculating the forces a bridge has to withstand or the arc of a ballistic projectile or any other calculations concerning primarily things on our planet.
I think that's a question of perspective. We, judging from hindisght and with access to more Information, can tell that. But the people signing up out of a misguided desire to serve probably didn't. Their motivation - regardless of result - was probably to do the right thing, which is a sentiment that Trump evidently doesn't just not understand, but doesn't even seem aware of. "What's in it for them?" betrays a fundamental ignorance of even the concept that his ilk leverage to get people fighting their wars.
Is that latch on the inside or the outside?