Just talking out my butt, but I imagine a shift in priority. Every documentary I've seen of people in the DPRK they talk about their hope for reunification because so many have family on the other side. With the US ramping up shitfest levels across the globe I can see how there could be a need to shift priorities and stance towards trying to seem as big and dangerous as possible. It's not as if the western world is responding to peaceful overtures anyway.