I lived in Scandinavia and saw the social situation frequently and personally. Sweden’s refugee acceptance rate was much higher than Norway’s for example.

You have groups of people from different war zones bringing their own intra group conflicts to a new country, compounded with those groups interacting and having to deal with each other, with both coexistence and conflict.

Regarding why they’re segregated, I don’t know for sure. But I suspect it’s a combination of people wanting to fulfill their social ideals with minimal upset to their existing standard of living. I’m also pretty certain there is some political division, as refugees are likely to vote for one party over another.