@Regulus Arcturus Black
You're missing the mark for several reasons:
1. In the case of Norway, just as many corona cases came from Austria as from Italy. We literally couldn't have had the winter break in Oslo at a worse time, as it was deemed unsafe to travel to Austria one week after people came back(my boss was one of them). Had the break been a week earlier, then they would have missed the outbreak. A week later, and they wouldn't have been able to travel there.
2. Secondly, you overrate the significance of the Norwegian winter break. The Norwegian winter break is really just a thing for parents of kids between the age of 6 and 19. For everyone else it's just a normal week. I think most of the people who traveled to Italy and Austria during that time did it regardless of the "winter break". It's basically viewed as a "second easter", because the weather is nicer in the mountains down south. A lot of people will also dodge the winter break week(s) because prices may jump during that time.
3. The Norwegian winter break is technically 2 weeks, not 1. In order for the country to not "shut down", one half of the country will have their vacation one week, and the other half the next.
Bottom line: Sweden hasn't been more unlucky than Norway. They just chose to do their own thing, and it seems like it didn't work(though it might change over time of course)