The way ship HVAC systems are designed, it helps limit costs while simultaneously increasing infections from anything that's airborne.

In regard to Diamond Princess though, there were no safety protocols that were followed, so we don't know if it was the ship or the failure to follow pathogen related protocols.

This virus isn't airborne. It's spread through respiratory droplets.

There have been reports that aerosol spread can occur in limited cases:

https://youtu.be/xWj9OUAfTLQ

As this and all other reports indicate, it can become aerosolized in certain invasive hospital procedures, which involve sticking stuff into people's lungs. This holds for a lot of diseases, we've known that for decades, and it doesn't have anything to do with how spread occurs in public.