The big world ending fear of the second half of the 20th century was nuclear holocaust, which suddenly felt a lot less likely with Gorbachev and the end of the USSR. The next dire thing that popped up was the hole in the ozone layer, which the world actually acted on and had stabilized by the late 90s. It wasn't until the 00s that global warming entered people's awareness. So I don't know I'd describe it as "delusion" to feel good in the late 80s to 90s when the major problems that people were aware of were legitimately getting better.