The ferry was a ro ro type, roll on, roll off.
they were banned in the EU after the herald of free enterprise capsized due to improper bow door use: water came in and only after a few feet, had enough to destabilaize the vessel, killing over 300.
This instance, the same is though to of happened. This, and the superstructure had around 7 floors added to is height. A stiff wind hitting side on could have been enough to tip it.
the only reason so many survived was because of relatively warm waters.
If that had been somewhere like the irish or north seas, then i doubt there would have been any survivors.