Sitting in the Oval Office behind the iconic Resolute desk in 2022, an animated President Joe Biden described the challenge of leading a psychologically traumatized nation.The United States had endured a life-altering pandemic. There was a jarring burst of inflation and now global conflict with Russia invading Ukraine, as well as the persistent threat to democracy he felt Donald Trump posed.How could Biden possibly heal that collective trauma?”Be confident,” he said emphatically in an interview with The Associated Press. “Be confident. Because I am confident.”But in the ensuing two years, the confidence Biden hoped to instill steadily waned. And when the 81-year-old Democratic president showed his age in a disastrous debate in June against Trump, he lost the benefit of the doubt as well. That triggered a series of events that led him Sunday to step down as his party’s nominee for the November’s election.Democrats, who had been united in …