“I wonder if the tunnel had a little “help”.”
The Chinese have been briefing every North Korean official they can that the entire facility is in danger of collapse. A full collapse of the site would spread radioactive debris across the border in China. The tunnels are at least two miles deep. That’s a lot of volume. It is doubtful China would help a collapse happen. It is doubly doubtful that America would, either, given that fallout knows no borders.
Would an internal collapse without any openings to the outside air release radioactive material? If a tunnel or two that is two miles deep collapses...? I am asking, as I really don’t know.