North Koreans, moreso than any other group, are taught to revere their leader as a god. Only the most devout ever get any kind of position with a decent life. Any North Korean who emigrates will see that their leader is not any kind of god, and might go through a crisis of "losing their religion" and fall into despair and drug use. So that's not necessarily attractive to Chinese or South Korean owners looking for new laborers.
The one thing all religions have in common is the ability to last thousands of years. North Koreans may be woken from this spell next month, or never. Or anywhere in between.

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