The primary people dying of Coronavirus are generally over 50 years old

This is one reason why so many were infected on the Diamond Princess while it was in quarantine in Yokohama, Japan. Because most people who can afford to travel on Cruises tend to be older than 40 or 50 years old generally speaking. So, they were more vulnerable to infection. Also, even though they quarantined the ship and had passengers stay in their quarters the ventilation system still brought air throughout the ship from all the cabins to each other still and the crew were NOT quarantined who were fixing the food for the passengers. The crew often didn't have their own rooms and had shared bunk rooms so it wasn't practical to isolate them in groups to their rooms

So, in some ways it was counterproductive to quarantine the passengers to their rooms in the end because you would have had to have quarantined the crew too which mostly wasn't possible and you would have had to do something different with the ventilation systems too to make all this practical as well. So, a ship is one of the worst places to be because of this in any epidemic or pandemic.