collapse of the old society

There is some path where collapse is enough to make people act but not enough to destroy civilization outright. Where the current system is overturned, and we all coordinate to survive. That's absolutely realistic. Not that it won't involve a whole lot of dead people, but the total decline would need a highly intense global event that crushes food output for a few years. A shallower version where food runs short enough to cause revolutions but not so much that a everyone dies quickly seems most pluasible. Obviously that will be choatic and whi knows what comes out, but not dying is very motivational, especially when you have glimpsed death.