It's purely human error mixed with over confidence, that "nothing will happen to me or my ship " . I have sailed in these area for about 14 months, with about a month in napoli itself. These guys do some daring maneuvers which a normal captain will not do in his wildest of dreams !
The sad thing here is about loss of life. If he had taken a decision to evacuate the ship little earlier he could have saved all the lives ! Since the ship is in shallow waters just mustering of all passengers as soon as grounding was enough.
But again, it is easy said than done !. The ship has just sailed (about 2.30hrs from port ) most passengers may be sailing for the first time on a ship. Since its night they wouldn't have done any briefing about safety or mustering ( crew would have thought to do it next day !). So, even if they would have sounded the alarm for muster, there may be many passengers who wouldn't know where to go !
So, just blaming the captain alone for the mishap doesn't sound correct here, the root cause may be the captain but there are soo many hidden causes for the incident.
Whatever be the cause many valuable lives were lost ! RIP .