To be clear, I'm not making accusations about Vietnam, I was just thinking about it and found it a little strange.
I can think of some fairly plausible reasons, but just because those reasons are plausible doesn't mean they're actually correct, so I was wondering if anybody had a more concrete historical and materialist understanding of the situation.
Multinational mining companies have been salivating over North Korea's natural resources for decades and would jump at the chance to get access the second sanctions were lifted.