Kurds have traditionally lived in the mountains and have been extremely good at defending them. Most of the post-roman invaders (Arabs, Turks, mongols etc) were desert/steppe nomads and lacked the skills or desire to repopulate hilly terrain filled w warlike Kurds.

Anyways, Kurdish is a linguistic relative to Iranian, so compared to other warlike hill people (the basques, etc. ) Kurdish isn't that different from its neighbors.

Also Kurds are majority Muslim and have been very well integrated into regional polities in the past (Salah al din/Saladin might have been Kurdish for instance).

I fought in in Kurdistan, for a group called YPG. This should be a fun read. Great question OP. Abdullah Oçalla. Touches up on this in "War and Peace in Kurdistan", and in "Roadmaps".