- I'm making it up. I'm not, but that would just be taking my word for it twice.
- It's true, and completely random. Seems unlikely.
- It's true, and Scandinavians have a magic low-crime blood factor, perhaps it adheres to the blond gene, next to the lutefisk-appreciation gene. That would be weird, huh? Not necessarily racist, but weird.
- It's true, and Scandinavian Americans have cultural continuity with their brethren in the home countries. That's pretty boring and normal, so this is the one I picked.
- It's true, and due to the Aryan superiority of the Nordic white race, which we must preserve so they can continue to dominate the swarthy people of the world.
You picked that one, not me. I think it's absurd.
- historical coincidence caused subgroup migration from those regions at the time, and there is cultural continuity with that subgroup
After all, Indian Americans are a remarkably tiny high-median-income, low-crime ethnic subgroup in America.
I agree. Given that Scandinavia was the homeland of the Vikings, I think arguing that they have a genetic predisposition away from crime would seem rather absurd.