The article I read said he’d been MORTALLY wounded. If ya gotta go, you might as well go out in a blaze — or a gurgle — of glory.
I imagine it would be highly difficult to maneuver a critically wounded sailor into the sub, and action had to be taken immediately. The time spent rescuing the skipper probably would have meant the death of the entire crew. But looking at the damage done by the ramming, it’s amazing that the sub managed to dive without sinking itself!
I doubt he had time to know his wounds were ‘mortal’. He only knew his sub was in danger and he did not hesitate.