ESPN actually ran a story about Manning's case in 2003.
Mike Freeman, who now writes for the Bleacher Report, published a piece in a Jacksonville newspaper in 2005.
As to why the network hadn't extensively reported about it until recently, I don't know.
Just like nobody really reported the allegations against Bill Cosby extensively until recently.
ESPN was not the only news organization who only gave scant coverage of this case before February.
The Big Lead mentioned it a year ago in comparison to the Jameis Winston rape allegation.
Other than that, not even Yahoo!, or other national sports websites, mentioned it either until the last few weeks.
Howard Bryant has a really good piece on this that was published yesterday.
http://espn.go.com/nfl/story/_/id/1...g-allegations-cam-newton-press-conference-nfl