Believe it or not there are a LOT of Christians in South Korea.
I believe South Korea has the biggest Christian churches in the world. The norks don’t have any, though.
Thing is, pre-and post-natal care matter. The current population of NK is stunted mentally and physically. They really will not be able to compete until they produce a “clean” generation. They’re kinda like the citizenry of so many African countries. You could clean them up and send them to school, and there is just not enough “raw material” there to really bring them up to the equivalent of the populations of the world that were properly fed in their early years.