Many words have been written about this incident but it's a simple fact that they had no way of evaluating the condition of the hull. Successful dives don't mean anything because all materials degrade and they had no way of knowing how much life and margin it ever had left. The acoustic warning system was a gamble because it provided no warning of failure modes that happen quicker than the vessel could surface. The more technical arguments only serve to muddy the waters if they're not framed as addressing these more fundamental and easily understood risks.