It seems that internet access from within the country is extremely limited, and the only people who have it are people already in positions of political power,

It seems that internet access from within the country is extremely limited, and the only people who have it are people already in positions of political power, who would stand to lose, not gain, from a revolt. Hackers could conceivably penetrate NK's NOC and seize control of it, but it wouldn't do much good since such a tiny number of people even connected to it at all, and those are the people who are already trusted and allowed to see the internet. Meanwhile, most people in the country don't have any kind of access to computers, and most of those that do, can only access the country's (allegedly air-gapped) intranet, which cannot be attacked unless someone inside the country physically connects it to the internet.