In Finland masks really became the norm only in late autumn but distancing, as Reuters said, is something we have been doing naturally even before the pandemic. People have been joking that the two meter requirement is uncomfortable close to other people.

Seriously though, according to Eurobarometer poll three quarters of Finns say restrictions have had no effect in or have raised their quality of life.

According to the professionals the biggest factor in keeping the numbers down now was the very efficient one month blockade of the capital area in spring, which prevented the virus from spreading to the rest of country before August. Thus we started the second wave from less than 10 daily cases nationally.

Contact tracing has been quite decent, and it's one of the metrics used for regional restriction schema. Basically the regional R-number and ratio of contact tracing define the level of restrictions in force on that region. But I assume Sweden does it similarly, so it's unlikely to explain the difference.

One factor discussed earlier is that Sweden stopped BCG vaccinations in 1975, while Finland only in 2006 and Norway in 2009. There were supposed to be studies in spring last year if BCG provided some level of protection against Covid-19, but I haven't heard from those since.