And Belgium and Ireland had higher deaths than Sweden despite heavy lockdowns.
I think the biggest factors tend to be how hard the nursing homes/aged get hit in different locales. Sweden's admitted they should have done a better job of that, while Germany's done a great job for instance. Sweden's population is over 20% of people over 65 while Norway's is a bit younger at 17% (which shows up in their relative death rates already 8/1000 vs 9.4/1000.
I think it's also different for places that depend on trade and foreign interaction and more travel means more starting points. Sweden is heavily dependent on foreign trade while Norway is heavy into localized natural resources (oil and gas)
And that isn't to mention how they are coding deaths by the virus as another factor.
There's a lot we don't know yet, but in any case, it was always the point that the lockdowns wouldn't change the area under the curve, and could instead prevent extra deaths due to health care systems being overwhelmed. Sweden's health care system has never been in any danger of being overwhelmed, and they don't have the looming questions of how to end the lockdowns.