There has always been a decent sized portion of the population that thinks the end is nigh, society is collapsing, etc

It's because imagining a future is scary, people don't like thinking about things that are as hard to predict and uncomfortable as a good future where things are easier and society smarter because it carries with it the certainly that current beliefs will be over turned and current struggles forgotten - its very unsettling.

People love to think they're at the high point of civilization and things will collapse because otherwise things feel kinda pointless and scary - especially the thought of everything we know and care about becoming irrelevant and opinions we carry getting over turned