Anon, how much do you know about North Korea/South Korea? See, the thing is many North Koreans are heavily indoctrinated. Even if they don't accept EVERYTHING Best Leader says, they still believe a lot. For example, one woman honestly believed that in the illegal South Korea soap operas she watched, ALL the cars in the country were brought together for outside scenes. They did this because they knew North Koreans watched their program, so it was propaganda. When she was able to get into South Korea, she, a woman indoctrinated for 50 years, was completely blown away by what she was seeing. South Korea also has a massive secret weapon that they use against the most heavily indoctinated North Koreans and infiltrators.
It's called a "supermarket". See, North Korean stores have almost no product and those that do often just have certain things for show not to sell, and North Korea tells its people that South Korea is even worse off. So when NK citizens go to SK stores and realize just how much SK has, even the tightest web of lies starts falling apart.
Again: SK breaks NK indoctrination with fucking supermarkets.
Now, consider all this. Read your post again and wonder if you don't look like a bit of a twit with your "it's unbelievable that a thoroughly indoctrinated person might start cracking when confronted with contradictory information" line.