THE trial and conviction of former Minneapolis policeman Derek Chauvin for murdering George Floyd came with America at a crossroads, a moment of anguish, but also of possibility, which historians and activists compared to the Civil Rights era. From policing and race relations to the criminal justice system, the three-week trial of Derek Chauvin became "a symbol and stand in for our emotions, our fears and our hopes surrounding this whole set of issues," said David Greenberg, a professor of history and media studies at Rutgers University. The audience for the trial was hard to measure, but likely vast because…