Relations may have begun to thaw at or even before the olympics, where the two countries had a united team and their representatives seemed cordial to each other. While Pence sat right above (behind?) Kim Yo Jong and didn’t speak a word to her, and pointedly didn’t applaud the Korean athletes.
If, as reported, the mountain where they’ve been testing has collapsed or is imminent dange of collapsing, that is the most logical explanation for them backing off any outward display of their nuclear program... for now. As Kate said, those nukes are still their insurance policy.
Even if there’s peace between the countries, people from them won’t be freely associating - NK has too much invested in decades of propaganda to let any free ideas mess up “a good thing.”