Societies that have failed despite having lots of resources because of cultural deficiencies or lack of intelligence, well, that could be applied to the whole of Africa. But that's really opening a bad can of worms ;-)
I can imagine it's because it is very easy for corruption to absorb the wealth. The government has full control over the mineral rights of its land so authoritarian governments spend all of the money on foreign goods because they don't care about their domestic economy and simply trade the goods in USD [1] or some other stable currency that isn't tied to their country.
If you go into race war here we're going to have to ban you again.