It’s quite clear if you read the article:-

Buttigieg announced his 2011 campaign two weeks after Newsweek featured South Bend as one of “America’s Dying Cities.” People had been promised a return of manufacturing jobs for almost half a century, Buttigieg says — “a little like Trump in coal country.” From 1902 to 1963, the city was the home of carmaker Studebaker, which employed nearly 25,000 local workers at its peak, before going belly-up. The city never recovered. When he was growing up, “a lot of people would still talk about the closure like it happened yesterday,” he says. “When I ran, we had to paint a picture of the future that did not translate into nostalgia.”

For the residents of dying town and cities, the decimated rust belt, “America is already great” rang hollow. Pete is quite clear Trump was lying: The old coal mining and manufacturing jobs were never coming back.