Earlier quoted context omitted.
Lots of people predict lots of catastrophes. The trick is identifying the correct ones ahead of time. This is much more difficult than you are implying.
I think it's still very simple. We can view it through the concept of discount rate [0], basically people don't value a future event as much as a present one. The world ending in 50 years is not worth making drastic efforts now, at least for most people. If your prediction is too costly on the short term, as accurate as it can be most people won't act on it. [0] https://en.m.wikipedia.org/wiki/Intertemporal_choice
If you describe a situation in too dire terms, people will conclude nothing can be done about it and do nothing. On the other hand, if you describe a situation in too rosy terms, people will conclude it will work itself out... and do nothing.