One thing to note is, when we say that civilization vanished, it sounds drastic. A lot of ancient events such as fall of Roman empire etc also sound like it happened over a few years. However, the current changes happening worldwide are much more rapid than those ancient events.
What we face is a much more literal fall: massive extinctions of bio-infrastructure that we depend on for food, large swaths of land becoming uninhabitable without air-conditioning, etc., all within a couple generations.
