Societal collapse has happened before, many times actually (but usually with great spans of time between them). Western culture doesn't particularly like to speak about it, lest people get the idea, such cataclysm might repeat.
A society doesn't exist after it collapses, so "reporting" on it is usually rather scant and framed from the view of those left to talk about it (often not many).
Consequently, historians struggle with pinpointing the reasons for those collapses. People often had no clue themselves and didn't see it coming. Complexity theory is a rather new development.