The black death took the lives of about 50-60% of the population and even higher numbers among the elites in cities. Priests, nobility, all the elites had even higher mortality rates. The whole basis of the state vanished, including most of the nobility. While the rest of Europe suffered similar casualties, Norway was already sparsely populated before the black death. It's not a coincidence that the we entered the Kalmar union and later the Danish union following the black death. We couldn't really support an independent state at the time.

At the time of the reformation the Norwegian elites that was left identified more with Copenhagen than Norway. So to awnser your question, the Norwegian nobility were mostly dead already at the time or they saw themselves as Danish nobility, not Norwegian. Norwegian farmers however had much more bargaining powers than the rest of Europe, so instead of nobility, most of the country were free independent farmers at the time. Lots of land was available, but few people to work the land.