Honestly, that may not be the case at all. I think if they had reported it at the time, contacted police and had the perp taken off the ship in Port Canaveral it would have been a bigger story for two reasons:
1) Immediacy. It just happened - as opposed to something that happened last summer.
2) Pictures. Pictures, pictures, pictures. Pictures of the flashing lights at the ship, pictures of the guy being led down the gangplank in cuffs, pictures of curious cruisegoers peering over the railing, wondering what's going on.
I think there's an understanding that the story will be damaging either way. However, they are choosing the least damaging approach, PR-wise. Which also happens to be the most damaging approach in terms of the human toll.