It's true that poverty and education are factors in those things.
BUT in Islam, Quran supports the marriage between cousins:
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Wikipedia:
"Muslims have practiced marriages between first cousins in non-prohibited countries since the time of Muhammad. In a few countries the most common type is between paternal cousins.[170]
Muhammad actually did marry two relatives.[16] One was a first cousin, Zaynab bint Jahsh, who was not only the daughter of one of his father's sisters but was also divorced from a marriage with Muhammad's adopted son, Zayd ibn Haritha. It was the issue of adoption and not cousinship that caused controversy due to the opposition of pre-Islamic Arab norms.[172]
Many of the immediate successors of Muhammad also took a cousin as one of their wives. Umar married his cousin Atikah bint Zayd ibn Amr ibn Nifayl,[173][174] while Ali married Fatimah,[175] the daughter of his paternal first cousin Muhammad and hence his first cousin once removed.[176]"
And yeah those sources seem to be anti-Islamic, but the report is real. And the problem is real. Here's a more neutral source:
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'Bradford is very inbred': Muslim outrage as professor warns first-cousin marriages increase risk of birth defects
"Professor Steve Jones, from University College London, said the common practice in Islamic communities for cousins to marry each other increased the risk of birth defects."