Mix legends based on true stories with the continuous destruction and natural disasters that have befallen humanity since the beginning, and you have the recipe for divine Judgement reigning down on evildoers. If a solar flare strikes the Earth, killing two thirds of the population, it would be especially damaging to the decadent city dwelling consoomers, compared to rural people who are more prepared - separating the wheat from the chaff so to speak. It may not actually be God doing it, but our descendants would frame it that way.