Societies in that area of the world follow different family and mating patterns. They’re organized more patrilineally along the father’s line, resulting in what’s called Father’s Brothers Daughter, or FBD marriage. It’s where cousins marry within the man’s family, so if a man has a son, the son would marry his dad’s uncle’s daughter, which essentially creates a band of brothers.

I’m guessing the Islamic Revolution promoted this kind of traditional structure that’d probably been in existence for generations. Perhaps the resistance to the shah wasn’t so much about modernity as it was about upsetting the patriarchy by giving women rights. The revolution may have been a backlash against modern changes in spite of a thriving economy under the Shah.