There's no such cause, poverty happens naturally. Just sit on your ass and do nothing and it will come to you.
Wealth is what requires work and something to cause it, poverty doesn't.
It's somewhat awkward that the poorest places are the naturally richer ones, but when the world let you live with minimum effort that's what you do, and by doing as little as possible poverty will find its way.
I can highlight 5 causes of poverty:
1 History
Many of the poorest nations in the world were former colonies from which slaves and resources had been systematically extracted for the benefit of colonizing countries.
Not really. They still have most of the resources and slaves, actually even more slaves than ever. But it doesn't make any difference when the management is what it is.