Nordic equality is as natural as the inequality we see everywhere else.
Once upon a time, it was so. Today, not so much. If that's a good or a bad thing, it's an entirely different can of worms. I think diversity in the Nordics is beautiful, but Japan has managed without it and they have great artisans.
In the Nordics, in addition to long barbaric winters, having long barbaric Middle Ages helps foster social discipline. See what beloved King Vasa of Sweden did to peasants that weren't happy with their Gini coefficient:
Something like 25%-32% of Sweden is non-ethnic Swedish.
Maybe once upon a time they were homogeneous, but they are probably one of the most heterogeneous countries (outside of the New World countries, which are an entirely different category), though I'd wager most of Western Europe is catching up (see: UK, France, Germany, Belgium, Spain).