It seems that in the end, they just gave up and moved away south rather than dying out. There may be a bit more to it than that. The better known cliff dwellin

It seems that in the end, they just gave up and moved away south rather than dying out. There may be a bit more to it than that. The better known cliff dwellings have unfinished meals and chores that were simply abandoned midway. I stayed at a B&B which had an archaeological dig on the grounds, and read the report about the dig, which was on the coffee table. There was evidence of cannibalism. The diet the Ancestral Puebloans ate was prone to certain deficiencies which could be overcome by supplementation with meat. A climactic shift could have caused difficulty in obtaining game. The archaeological report made references to a theory about a secret society/cannibal cult, whose members became more powerful in part because they were the only ones around who weren't undernourished. So it's not just that they gave up and left. Life might have become weird and crappy in some frightening ways before they managed to leave.