Not that it changes anything, but is it known what the Crystal was attempting? The animation looks like it kept trying to pass ahead of the Fitzgerald for an impossible port to port passage. Or was the Crystal totally unaware of the Fitzgerald?
The Crystal had the right of way. By COLREGs, they were supposed to maintain their course and attempt to convince (via radio, horn, and signal lights) the other ship to give way. They were going half the speed of the Fitzgerald, and were much less maneuverable with far less power driving a far heavier vessel. This is like asking why a train ran into an automobile parked on the train tracks.
It's possible that nobody was on the bridge. Loads of tankers are driven by autopilot. Additionally, the USN ship wasn't transmitting AIS so they were essentially invisible.
