How was it possible for the military to entrust to a lowly Pfc (Manning)...?

extensive amount of super sensitive material over a period of time? What kind of special qualifications did Pfc. Manning have for the military to allow him access to top secret doents over a period of years? I was a commissioned officer aboard ship in the US Navy and I couldn't gain access to the radio room. What does this tell you about the quality of our security? And why hasn't the media question Pfc. Manning's accessibility towards these sensitive military and diplomatic doents. Someone higher up may provide some answers to this.