I don't think that South Korea was desperately poor 50 years ago because Koreans were innately stupid, any more than South Korea is wealthy these days because Koreans are innately intelligent."
Countries are rich or poor based primarily, if not exclusively on the relative amount of freedom their peoples enjoy. The two Koreas are a perfect case in point, as were East and West Germany.
Many nations in Africa are riddled with valuable natural resources yet can not feed their own people. My own state of Louisiana was far and away the wealthiest state of the antebellum south. It's endemic corruption and cultivation of dependency in the post-reconstruction era has left it amongst the poorest states in the entire US.
I think that's part of the story, but it's not anything close to the whole story. Just for starters, look at Equatorial Guinea and India. India has been a multi-party parliamentary democracy for 60 years, whereas Equatorial Guinea is one of the least free, most repressive countries on earth.
Yet Equatorial Guinea is the world's wealthiest country, measured in terms of per capita GNP, and India is, despite recent growth, still very poor. In this situation, the difference is natural resources, but there can be any number of things at play.