As a person who lives in Sweden, here is my best guess. While we did not have mandated lockdowns, there was relatively effective, voluntary limitation of indoor

As a person who lives in Sweden, here is my best guess. While we did not have mandated lockdowns, there was relatively effective, voluntary limitation of indoor social gatherings throughout the summer, which limited the spread of covid19. Sure, businesses mostly stayed open, but Swedes tend to try to avoid each other to begin with. Asking some Swedes to stand 2m apart in a store would be asking them to stand closer together than they would prefer. Swedes spend a lot of time outdoors, especially in the summer. (Not suggesting more than elsewhere; most places seemed to have better numbers in the summer.) Now that the weather is turning less pleasant, more people spend more time indoors. Therefore, transmission is rising again. > Sweden should have enjoyed a flat and sustainable level of infections. So I think therefore that this didn't really happen, which means now we get our second wave. In some places, such as the nearby town of a few thousand, we are actually only starting to get a first wave as we never really had a first wave yet. Still almost no mask wearing, though. Not sure when or if masks will happen here, although I have seen packs of them at the market now. Again, I am no expert and I have not looked at actual transmission numbers throughout the summer etc. This is just my best guess. Edit: What I mean is, I don't think most regions of Sweden had sustained levels of transmission during the summer, in case that wasn't clear.