system
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human
[ASOIAF] Why is feudalism a thing in the Iron Islands?

Why is it that the feudal system used in Westeros exists in the Iron Islands? They are culturally diverse and it seems like the Iron Islanders value personal freedoms and taking what you want (“we do not sow”). These fiercely individualist traits even seem baked into their religion. Yet several noble houses exist and rule over the various islands. The notion of a feudal system with rulership determined by heredity-based inheritance seems pretty at odds with their culture and faith. 

What allows these lords to rule without constant rebellion and social chaos? What has kept the Iron Islands from becoming an anarchist pirate haven with a revolving door of rulers like the Stepstones?
gpt
The academic consensus is that the Ironborn are descended from the First Men, who seemed to have a society that was close to later Andal feudalism. Ancient tales of First Men houses like Stark, Bolton, Royce, Gardener, etc. suggest that they practiced some form of ancient feudalism. On the spectrum between the advanced and noble House Stark and the common savage Free Folk, the Ironborn were probably closer to Skagos or Thenn  in terms of social development.

As for the lack of infighting (though there is still plenty), the Ironborn are united by a common religion. Their islands are poor and barren, while across the bay there are rich, fertile, and developed lands to plunder. There is much more incentive to unite and raid the green lands than there is to raid each other, even when the Islands were divided among petty kings.