Like many "disasters", its a combination of multiple "little issues" all cropping up at exactly the wrong moment in time that leads to "the well planned system" being overwhelmed and failure occuring.
Luckily in my time at sea, most were remedied at the little issue phase, apart from a very large vehicle deck fire that was caused by external circumstances. A vintage car on a trailer caught fire and spread rapidly as it had a fibreglass body and was parked next to a curtainside trailer. Fortunately, crew training and a very heavy duty sprinkler system extinguished it in about 40 minutes. The adrenalin rush took much longer to subside.