It’s not that the ruling regimes became corrupt and unable to manage or perform the necessary government duties. It was the volcanoes.
I just glanced at it, and I can’t help note that all the data stops at 1911. What, no earthquake in 1949? Weird that when the technology and recorded history gets better at recording actual volcanic eruptions, the charts stop.
I am skeptical about anything about China, especially speculative scientific work by Chinese scientists or historians.
(I saw the link somewhere else first, but it also appeared at Instapundit where Professor Reynolds uses it to advocate for space colonization.)