I think inbreeding is more a symptom than a cause. The cause is that much of the middle-east is a one-resource area. When you've only got one real industry, it becomes easier for the corrupt to get a monopoly on that one industry, and then make the locals so dependent on that one industry that they act against their own long-term interests. It is why so many small towns vote Republican: small towns often have one industry that sustains the entire town. That one industry threatens to leave if it doesn't get all kinds of massive deregulation and tax-breaks, and the locals side with that industry and truly hate any group that threatens to make it leave via regulation and taxes.
In the case of most middle eastern countries, aristocrats or theocrats control the oil, they use that to completely control the country, and the country turns into the sort of shithole you always get when one group of aristocrats or theocrats controls everything.
On top of that, you've got America propping up the Saudi theocratic aristocrats, who use their influence over America to blow up or destabilize any country that threatens their power or the status quo. America talks about being against theocracy and aristocracy, but the reality is that we are supporters both in the middle east, so long as they ally with us, either directly or via being allies of the Saudis.