Europe, America, China and even Russia have mercenaries corps (e.g. Glencore) that help African countries choose the right rulers, and when the ruler isn't right he gets replaced. The right ruler needs to be a chaotic plutocrat who cares only about himself and looks the other way when his home country is looted. As for IQ, it's a side effect of the above: NK and SK are the same people who live under different rulers for less than a century, but NKs are already much shorter. My guess is that in a hostile environments, the smarts and height genes stay dormant.