Why is not a question to expect answers to with only partial info. It could be their healthcare system (extremely socialized) is to blame to some extent. It could be that they were in a period where travelers from other impacted areas or Italians travelling to impacted areas were much higher than other places. It could be due to the overall age of Italians (5th oldest in the world at 45.5 median age). It could be their population density (200 per sq km) It could be a mix of all of those. Personally, I would bet a mix between high travel rates (and lower border control) and high median age and high population density. By contrast, the US has a median age of 38.1 (61st) and a population density of 34 per sq km.