Nearly every authoritarian country starts with people promising good things. A lot also start with rebels fighting against a group that led a massacre. They're underdog groups with popular support.

Then those underdogs take over. They become paranoid about the possibility of being killed themselves, so they repeat the massacres they fought against. A lot of people who supported the new regime think it's just a few remaining enemies being taken out. It won't happen to them. Then the government starts laying out methods to solidify their control. The list of things seen as traitorous and against national interests grows. It becomes a frog in a boiling pot situation. By the time people realize they might be a target, the system is too complicated and widespread to take down alone, and a new generation of youths have been raised knowing only the current system. And to those youths, things are stable. The most terrifying thing to people raised in stability is the idea of losing that stability. So keeping your head down and following the law is much better than absolutely anything else.

And with the absolute control of information that NK has, a significant portion of people really don't even know a better world exists out there. And they're terrified of anyone that even talks about shaking things up.

It looks like a liberal fantasy. The truth is that along the rivers that run on the border with China there are posts with machine gunners every 100 meters. Brainwashing is obviously nearly zero-effective, since they have to resort to machine guns.

Not limited to non-Western countries btw. We are also vulnerable.