I don't think you can entirely discount the effects of 20 years of Cold War existential threat, accompanied by duck-and-cover videos and the like. People were terrified and fascinated by nuclear technology - this is the era of Godzilla, and of mutant superheroes. Yes, there was a utopian vibe as well, courtesy of a concerted propaganda campaign [1] - but when the eco-movement kicked off in the 70s, nuclear was right in the firing line. That didn't spring from nowhere - it was decades of accumulated fear finding an expression.

[1] https://en.wikipedia.org/wiki/Atoms_for_Peace