No need for theories, the disease is more fatal to those over 80 y.o. That's why the mortality is higher: demographics
Germany has 700 cases and 0 deaths. Austria has 80 cases and 0 deaths...both of these countries are adjacent to Northern Italy region, in which 233+ have died.
Saying "no theory needed" frankly raises more questions than provides answers.
When was the 1st case in Germany and when was the 1st case in Italy?
it's ~ 4%