The CO might not have been on deck...he could gave been on his way to the bridge..
..on a stairrail....passageway....close to impact area.....a collision with a cargo ship 7-10 times larger than the Fitzgerald..is gonna rattle things...including bones
I’ll bet his stateroom is right there at the impact point. There are four staterooms on the main deck, 2 on the starboard below the navigation bridge. He was probably asleep when the ships collided.
Not having been on an Arleigh Burke class, I’m guessing that is Officer Country.
The others could have been in the damaged and flooded accommodation spaces.