North Korea is already fairly good at avoiding sanctions. The entire economy is planned and organized by the government. For North Korea it is incredibly easy to just completely shift gears and circumvent these sanctions. Obviously without any sanctions, that would make life a lot easier in NK, but I do not think that this is the main reason for this shift in policy.
There is also not to much point for NK to get fewer sanctions in the first place. They would only really profit from less sanctions against import/exports of military goods, but it is not like that is going to happen any time soon.
For non military goods, it is not like NK is all of the sudden going to import goods from all over the world. Even if they were allowed to, they would not do that. Kim Jong Un and his henchmen have to keep the population in place, otherwise they are soon going to be history.
