Well even then, if you actually looked into this sort of thing, its been obvious for a while.
Historically, as studied by anthropologists, historians, sociologists, its been known for a while that civilizations collapse due to:
Massive Famines
Unexpected Broad, Rapid Climate Shifts
Massive Internal Political/Civil Unrest
Foreign Invasion
Massive Plagues
Insulated Ruling Class making absurd decisions to maintain their own power at the cost of the actual stability of their society
Collapse of Vital Trade Routes
Neglect and Failure of Vital Infrastructure
Financialization of the Economy, writ large
…
Now sometimes it can be just one of these, but usually its a few.
Most current societies/nation states are currently experiencing or will very soon be facing nearly all of these combined.
I suggest you read John Michael Greer’s Catabolic Collapse book or watch some of the videos about it for an overview of the basic idea that complex societies tend to respond to crises by becoming more complex, which is the exact opposite of what you would want to do from a big picture, hindsight perspective, but is more or less unavoidable due to human psychology and socio/political/economic dynamics of human organized societies.
…
You are right that the vast majority of people will be surprised by the speed of collapse, logarithmic vs linear basically.
But the people who have been in charge of our societies either did, do, or should know or should have known about this.