No one foresaw the ultimate collapse of Nate Parker’s “Birth of a Nation” after its stellar reception at the Sundance Film Festival last year, when perfect timing, immense hype and a vigorous bidding war resulted in a record-setting $17.5 million sale. One year later, as Sundance begins again, “Birth of a Nation” isn’t exactly top of mind for many – at this point a distant story as its would-be awards run suddenly dried up.