There are also cultural differences, Italians like to hang out in groups, outside, personal space is much smaller, people hug and kiss and touch all the time. Also they're not really the most disciplined nation, lots of them simply ignored the safety rules, continued to go out, there were even some cases where infected people run away from quarantine.

And additionally the spread of virus is not uniform as it depends on social circles, so it's very hard to compare the situations using just general population stats. In South Korea one of the early patients infected more than a thousand other people, while some patients infected no one else or only a few. It's totally random event, and a few patients like that can create a huge differences in the spread of the disease. In Italy they've had the bad luck that early on virus got into hospitals and retirement homes, so the most sensitive population was massively affected.