An interesting thing about the Helge Ingstad is that two important aspects of the incident, the AIS and flooding are at completely different levels of safety defense.
It could be likened to sports, a soccer game for example.
First line of defense is to keep the ball in your possession and at the opponents end of the field. That would be keeping the AIS on.
Excess speed, then lack of situational awareness - the other team gains possession and works the ball down the field.
The last line of defense is the goal keeper stopping shots on goal. Last ditch defense. That would things like emergency generators then last, watertight integrity. In this case the failure of the watertight compartments breached the last defense.