Investigate and charged are two different things.
Ah... I think you need to recheck your timeline. The US military first announced an investigation was underway on January 16, 2004. In February they announced that a number of soldiers had been suspended from duty. In March they announced they had laid initial charges against six soldiers.
Through all of these announcements the media expressed very little interest at all. It wasn't until April 2004, when 60 Minutes released a documentary on the abuses, that anyone actually cared. By then prosecution was well underway. Even then, interest was muted.
Then in May 2004, when the US Military released the Taguba Report which contained the findings of Major General Antonio Taguba's investigation the firestorm really sparked into life when a number of high-profile media outlets (most notably the
New Yorker and
NBC ran articles. Their articles were based almost entirely on the report released by the US Government.
Abu Ghraib is actually a perfect example of the military being pro-active in identifying abuse, stopping it, and being open and honest about its existence.
(Having said that I feel like they weren't aggressive enough on the prosecution side of things, though there were procedural screw-ups like most charges against Lieutenant Colonel Steven L. Jordan being dismissed because the interviewing officer failed to read him his rights.)