Well it would seem that African nations have been cursed with many corrupt and incompetent leaders.. The greater problem and the reason why these leaders hold onto power far longer then they should is because Africans are told that all their problems are the result of imperialism / colonialism, that the white man caused everything to go bad.. Sadly many African people believe this and so they never focus on their leaders as the problem, they focus on Europeans as the problem.. So the problems continue because the real source of the problem is never dealt with..
Similar thing happened a lot in Europe.. corrupt and incompetent leaders telling their people that all their problems where caused by the Jews and many of the European population believed it.. Corrupt and incompetent leaders like having scapegoats to direct the peoples frustrations and anger against.. Takes the heat off them if someone else is getting blaimed for the problems..