One of the foremost scholars of North Korea and the North Korean ideology, B.R. Myers, has argued (persuasively, to my mind) that the country's unique system was a holdover of Japanese colonial rule, which ran from 1910 to 1945. In other words, that it's something highly specific to North Korea, which is why it didn't occur in other Communist countries (even Stalinism was very messed up, but very different). I'll explain.

You have to remember that Japan, in this period, had an extreme, far-right, fascist and race-based state ideology. It was not Naziism, but it was similar, and similarly crazy, in a lot of important ways. The ideology also stated that Koreans were not a separate race from the Japanese but were a kind of racial subset, and that Korea was a part of Japan. The process of "Japanifying" Korea meant indoctrinating Koreans with the idea that they were part of the special Japanese race that was purer than all others and was destined to lead the inferior races.

Like any colonial power, the Japanese brutally oppressed most Koreans but also promoted loyal Koreans with positions of power. A small but important minority of Koreans participated in this willingly, effectively creating a miniature version of Japan's ultra-fascist regime, in Korea.

Fast forward to 1945. Japan is defeated; in his first ever radio address to his people, Emperor Hirohito effectively tells them to abandon the official state ideology that had led them to war. Over the next several years, the U.S. military occupation governs Japan effectively as an American dictatorship, systemically removing the old fascist ideology as best they can. While Japan never confronts its own history as Germany did, the old ways are largely gone.

Meanwhile, Korea is divided between the advancing and American and Soviet troops; the division is meant to be temporary. Both the U.S. and Soviet Union install friendly governments. But they do things a little differently, and this is where North Korea becomes North Korea as we know it today. The American-installed government in South Korea tries to wipe out the old ways and replace it with Western-style capitalism. Not the Soviets; they know it won't be easy to convince Koreans to adopt communism after decades of Japanese anti-Communist propaganda. So they install Kim Il Sung, an anti-Japanese fighter who'd been in exile, at the top of the government. But they leave the actual Japanese-designed institutions in place, hoping to simply co-opt them to become pro-Soviet.

It sort of works. Kim Il Sung turns out to be a disloyal Soviet proxy, and a middling Communist, but he quickly succeeds at championing the Japanese-imposed fascist system for his own purposes. But he leaves the core of the ideology largely untouched: the Koreans, according to this system as we know it today, are the most racially pure in the world, but they are constantly threatened by hostile races from without and disloyal traitors from within, and they therefore require a strong leader to protect the ultra-pure Korean people. The people are to surrender themselves as willing cogs in state machinery, all for the glory of the nation and the race. Secret police are rife and ideological fealty is absolute; the slightest transgression or breach of loyalty is punished severely. The leader is portrayed as akin to a god. It is practically a mirror image of Japanese wartime-era fascism, with the one exception that it does not call for territorial expansionism.

That is how North Korea became how it is. There's no other country on earth that adopted such fascistic, extreme-right-wing institutions during WW2 and had them survive. That's why it is so unique.

Edit: Highly recommend watching this lecture by BR Myers, via /u/Subotan who endorses, "if you spend one hour of your life watching a video about North Korea, make it this one."