Rampant automation starts crashing the economy by replacing jobs and ruining the environment. People (largely miners) protest. The protesters are unsurprisingly demonized as commie traitors. Eventually a ton of them secede from the US (the "free states" movement) over it's blatant corruption and form a loose anarchist society (the exact details are vague) in their own private fallout shelters while everyone else treats them with mistrust and keeps drinking the conservative pro-America koolaid to the very end.

The bombs drop and all those same people, whoever is actually still alive, hypocritically turn to the free states people for help.

Fallout 76 is weird in that way. In most ways it's not a Fallout at all, yet in some ways it's closer to the originals than 3 and 4 ever were.