My take is that there were a series of disasters, some perhaps not recognized as such. While the Bubonic Plague, Mongolian invasions, or the fall of the Roman Empire were rightfully recognized as disasters, I think also that many of the political systems of the day, eg, the Roman and Byzantium Empires, the Roman Catholic Church of the Middle Ages, and the Ming Dynasty helped contribute to the stagnacy of that era.

This is why I consider stagnation or collapse to be one of the key threats to human civilization. Even now, everyone knows generally what sorts of technologies and systems work. But too many parts of the world still use systems that devalue human labor and ingenuity.