I think mass hysteria is too perjorative. We have a lot of suspicious data points, but then a new data point turns up (early lights were a false alert) which suggests that the data generating process may be pretty biased.
Definitively not coincidence, but there are a lot of things that could cause a pattern of reported air lights - such as a warning to be on high alert looking for them, the autumnal equinox (nights are getting much darker very quickly in Denmark right now), etc.
Beyond the fine, the airlines will try to get their losses in millions back from someone. If it turns out to have been a private person, there will be lawsuits. In general parents are liable for their children. When a child is old enough to fly a drone on its own, I think it will also be of partial-legal age. Acceptance of manslaughter and threat to national security is not taken lightly.
The 4 other airports were all in DK, where it's top of the news and where everyone is talking about it. Not in other countries.