Because Italians IGNORED safety suggestions. They did not change any habits. They kept going out to restaurants at night, old guys hung out at their cafes, kids were allowed to play in the squares and then go to their grand parents and infect them, etc., a terrible chain of transmission. No one wanted to change their lives one bit.
This is how local residents describe what really happened.
We cannot allow this to happen here. I think that guy on the plane should be prosecuted for endangering the lives of others.