> At peak, we had about 80k nukes (way less now). That’s nowhere near enough to kill all 8bn people (as spread out as we are).

Directly? Probably not. But the contamination from fallout is more than sufficient to poison a significant fraction of humans over a not-too-long time horizon and provide everybody else with a significant cancer risk. The ensuing chaos and resulting breakdown of civilization will do the rest. Don't believe it? Ever seen the panic when toilet paper is at risk to run out at Walmart?

Those who still remember the Chernobyl disaster are aware what that meant for Europe. A single plant, and everybody got warned and could take precautions.