The Norse immigrants did not understand how a place that looked so much like their home, possessed a very different climate. They'd arrived in a milder spell and thought they could recreate their homeland's domestic environment, with cattle and other familiar things.

They disdained eating like the natives who they had shunned. They had their ruling class whose system of sending wealth back home for their prestige, impoverished other parts of their society. Near the end of the collapse due to the harsher weather, lack of diversity and failure to adapt, the poor were dying from starvation.

They slaughtered and ate the rulers. But chances are it won't happen that way again as society is much different now. That was an isolated ecosytem and society, just like the examples of Easter Island and other lost societies.