TEN YEARS AGO TODAY, in the middle of the presidential campaign, an essay in The Atlantic set out to explain the appeal of Donald Trump. Its author traced that appeal to the social decline and cultural trauma he had known firsthand, in an impoverished childhood. The author, J. D. Vance, had only days earlier published Hillbilly Elegy, which went on to sell roughly 3 million copies and made him, almost overnight, the country’s designated interpreter of working-class grievances. And he was quite g