These's no proof of that. Vietnam was at war, and a very brutal one to say the least, of course it could only properly develop after peace was signed. North Korea already has de facto peace, it's a completely different situation.
Are the odds against Pyongyang? Certainly, but it's definitely not impossible to reform and prosper even with the South continuing to exist. The alternative is an eternal stalinist dictatorship despised by the whole world. The more we take to reform the country, the more it will be vulnerable to the inevitable tribulations of opening up it's economy and the more problematic the reform becomes.
There are nuances here - these days, South Korea is faced with difficulties caused by the destabilization of the international situation and the precondition for the formation of military blocs. South Korea is deprived of its own resources and, for quite logical reasons, relied on abundant exports and imports as the “Workshop of the World.” At the same time, the Seoul government built trade relations based on profit, neglecting any political obligations to the United States. However, the US military presence is the guarantor of the existence of the regime. And as a result, after the start of the American-Chinese “trade wars” under Washington, Seoul was forced to refuse supplies of electronics, which hit tourism (because the Chinese stopped visiting the country). Now trade relations with Russia are in jeopardy (after the war we acquired an incredible amount of Korean goods). The DPRK survived the situation in the city better, simply because in such conditions the PRC is ready to support them as a barrier against the United States.
So although the idea of complete autarky is absurd, the idea of self-sufficiency of the economy and “reliance on one’s own resources”, like many other steps of Pyongyang, was quite logical. Moreover, in the eighties there were “Joint Enterprise Agreements” with a number of Western European companies, as well as Economic Free Zones. As a result, this brought nothing, since the bourgeoisie did not see sufficient financial guarantees.
