Ah, but how hard would it be to persuade our beloved mahometan friends that they do have lands of milk’n’honey? And sharia too! What’s not to like?
Very hard.
Saudi, Kuwait, UAE, etc. have oil income for their own subset of a “native” population. These are really small countries - or the population/livable area is small, the rest is useless wasteland. They can be more or less wealthy if they don’t have to spread it around to all the billion + believers.