It is actually worse than that. There’s a bad tendency to MULTI-GENERATIONAL cousin marriage.
There are several factors pushing it.
When you marry a father’s brother’s daughter, she doesn’t have to veil in front of in-laws and family because they’re all legal guardians.
Your cousins are the only people you can both marry and go out in public with - i.e. date.
Since families tend to live together with paternal kin, she remains close to or next door to Mom, Dad and brothers - so she can actually get help and support from them instead of being at her husband’s mercy.
And there really isn’t a bride-price when cousins marry, whereas you have to pay for a bride you’re not related to. No money changes hands, either, when two relatives exchange two daughters so that each of their sons has a free bride. Thus economics is a MAJOR determinant. The next generation has cousins prone to marry each other, the very intertwined family tree making bad recessives likely to pop up.
In some of the pacific islands, where the men were often promiscuous, the uncle was the benefactor of the children and not the husband of the mother. Since paternity couldn’t be trusted, the uncle knew his genes were safely within his sister’s children.
This seems like another version of that.