Not at all surprising, given the instability of the government and the repressive brutality sanctioned by their Koran. I have read that many tribalists do not venture far away from the areas they grew up in, meaning it is common to be somewhat a blood relation of your spouse. I don’t know how true this is.
First-cousin marriages (generation after generation ...) are the norm in Iraq, Afghanistan, Pakistan, Ethiopia, and some other parts of the world. This is the case whether the people are Moslem or not. (Egypt and Ethiopia have significant Christian populations.) It’s about keeping control of property in the hands of the clan leaders, and the health results are ghastly.
One American doctor in Saudi Arabia called the Saudi royal family “an irreproducible laboratory of genetic defects.”