But the one thing South Korea had over all of them: the USA. The ROK was a US garrison state, and a military dictatorship well into the 80s. They were a major staging ground and supplier for the Vietnam war, and billions of dollars flowed through companies like Hyundai, growing them into industrial giants. The USA was even directly paying ROK soldiers who participated in Vietnam. The USA was eager to maintain a toe-hold on the Asian continent, and provided active support. When the "Arsenal of Democracy" needs a local supplier, you can create a lot of infrastructure.

Funny how I have read the same argument regarding Japan and the Korean War... (I'm not saying it is wrong, just that I find the similitudes interesting)