Average IQ. In a country there are genius and retard all residing on the same place. Thus, we have lecturers, street cleaners with different people holding different jobs depending on their abilities.
Nigeria, with a population of more than 200 million people. There are bound to have some smart folks there. Sinkie also have some silly folks among us. Smart able to con silly people. It is a matter of probabilities.
Average IQ is the main factor. If Nigeria have all the princes that you mentioned, they would be 1st world country by now. Not easy to guess as their AVERAGE IQ by just looking at their progress.
Race and IQ