Why Arizona's magazine explosion was not unique

Was the catastrophic magazine explosion aboard USS Arizona unusual for a capital ship?

No; once a main magazine detonates, catastrophic destruction of a large portion of the ship is a recurring danger rather than an Arizona-specific anomaly.

The scale of Arizona's destruction was tragic but not abnormal for a magazine detonation. A magazine contains enough propellant and ammunition to destroy much of the surrounding hull when it explodes. The short exchange distinguishes the unusual circumstances of Pearl Harbor from a damage mechanism seen in other capital-ship losses.