At a time when the US stands in front of a confluence of historic crises, former President Barack Obama has started stepping forward, emerging from his political hibernation and taking on an increasingly public role.   The US has been rocked by a series of crises that has exposed deep racial and socioeconomic inequalities in America and reshaped the November election, reports AP.   Obama is signalling a willingness to sharply critique his successor, President Donald Trump, and fill what many Democrats see as a national leadership void. On Wednesday, he held a virtual town hall event with young people to discuss policing and the civil unrest that has followed the death of George Floyd in Minneapolis.