Arizona was in port, which made rescue efforts easier. Further, when the Arizona settled there were still portions of the ship above water, which made survival more likely. The wreck only slowly settled into the mud under Pearl Harbor over the course of time, and the superstructure was cut off.
Barham was actually in the process of abandoning ship when the magazines blew.Anyway,I thought that the point was that Eurale was amazed that anyone survived the explosion.