Someone else has mentioned how they learn. As to why they do what they do, it's probably for the same reason people do most things: to get a better life for themselves and their family. I don't think they do this out of fear of becoming the victim, these are elite and well-trained operators. They volunteered to get this education, they aren't conscripts. As crazy as it sounds to you or I, I think these individuals genuinely believe in the DPRK, or at least are apathetic to it and think only in terms of their own advancement.