Fish that bites its own tail. North Korea is weird as it is because of the isolation imposed on it after the country was quite literally levelled by US bombings. That’s the historical and materialist events that gave rise to “juche” ideology in the way North Korea understands it now. I think you’d be pretty scared of outsiders if your country had been as close to literally entirely destroyed as it gets by foreign bombing, and if when you tried to rebuild your economy you had been subjected to an almost complete economic blockade.