Islam was born the harshest dessert and does best in the dessert and arid regions of the world. Back in Mohammed’s time the clan was all important for survival of the fittest clan in such a harsh water deprived environment. You stuck together or died.
Inbreeding cements clan loyalties. Also keeps dowry wealth within the clan. So there is a perverse incentive for inbreeding among the Arabs going way back. They are wealthier now so the desert does not look as harsh as it used to be...But the old time ways carry over.
Afghanistan is an arid nation. Clans are very strong there. It is hard to form a modern democratic nation when clans and tribes and extended families are so strong
Christianity and Judaism were born in that same region, but they grew up. I think the tendencies that you mention are more inherent to Arab / Afghan culture than to Islam per se, although heaven knows that Islam has its own, many pathologies.
I’m guessing that’s why Islam never caught on in Hawaii. Not only is it a tropical paradise, they have too many interracial marriages to suit Moslem tastes.