I'm not saying that there haven't been some good things to come out of this situation - people working from home and thereby saving gas, limiting pollution, etc.; increased awareness of basic cleanliness practices, particularly in some countries that are quite noticeably less fastidious than the US generally is; actual tests of some of our response mechanisms (I mean, you don't trust your backups unless you've used them...) - but the extraordinary response of basically shutting down Europe is so far and away over the top...
I don't pretend to understand _why_ people have freaked out like this, but I suspect it's pretty much in line with why they freak out about anything: they've been programmed to wait for the "next big thing" that is going to kill us all by news, TV, movies; the news has, as usual, plastered everything across the "front page" on a constant basis, essentially "hyping" it up; and probably that on some deep psychological level we've all gotten a little overwhelmed with technological advances and how quickly the world has become a global market that is "always on", so we were unintentionally waiting for some way to pull back and deal with ourselves for a while.