Comment by Arainach

It's not clear to me that that's the order of causality.

It's easier to be optimistic and to write optimistic when your society has high marginal tax rates and visibly uses those rates to combat poverty, fund research, and subsidize college (and when you're part of the demographic receiving most of those benefits).

When you see societal protections being stripped away and privatized, the suffering that was caused by that, and the callous nature of your fellow citizens who "got theirs" and continue to vote for politicians who attack and tear down the systems that enabled such growth and optimism, you're more likely to write stories shaped by that world view.

Dystopian fiction has a long history, but from stories I've read it feels like the inflection point was, as with so many things, the Vietnam war, which for many people shattered the myth of technological infallability.