Norway had (by necessity) access with boats to most of the population and were limited in land area. Far easier to control. But it was still a thin veneer 1066. :-) See https://en.wikipedia.org/wiki/Christianization_of_Scandinavi...

As far as I know, it was quite behind the rest of Europe and was on the brink of getting "integrated" culturally the 100-200 years after that?

Western Europe wasn't exactly Rome, of course. I should probably read up on European society around the time, before the plague. References welcome.

(Ah, it should have been more orthodox influences down in Constantinople.)