For the first couple decades while it was ahead of South Korea economically (in large part due to support from China/USSR) it was not that bad but during that time the system of absolute control by the Kim family was setup and once it was up it is too late to really do anything due to how absolute/brutal the control is (you say anything wrong and you and your whole extended family end up in a prison/death camp)

Basically people are willing to put up with a lot if their lives are getting better (economic growth). Problem with that is what kind of system of control an authoritarian government can setup in that period of growth.