[flanbiscuit]

To me, it seems like it was because of wars and raids.

from https://en.wikipedia.org/wiki/Derinkuyu#History

> refuge from the raids of the Umayyad Arab and Abbasid armies, during the Arab–Byzantine wars (780-1180).

> The city continued to be used as protection from the Mongolian incursions of Timur in the 14th century.

> After the region fell to the Ottomans the cities were used as refuges

> As late as the 20th century the town's inhabitants, called Cappadocian Greeks, were still using the underground chambers to escape periodic waves of Ottoman persecution. (The Cambridge linguist Dawkins, who spent time in the towns from 1910-1911 while writing his book on Cappadocian Greek wrote, "their use as places of refuge in time of danger is indicated by their name καταφύγια. In 1909, when the news came of the recent massacres at Adana, a great part of the population at Axo took refuge in these underground chambers, and for some nights did not venture to sleep above ground

[boomboomsubban]

Though it wss built to protect from raids, keep in mind every instance of it's use you list happened at least a millennium after it's creation.

[therein]

Yeah, definitely not cataclysmic events. Never consider that. Always persecution.

People would run away from persecution. Not hide underground at the spot they expect to find you.