Usually it means he plead guilty to get reduced charge and not go to trial. I would hope he would have had to inform truthfully on his co-conspirators to obtain the reduced charge, though its not a requirement to make such an agreement. In normal law cases, if the prosecutor can get a plea agreement, he gets his win without risk of losing t trial, so might do it just for that reason. I dont think this case is typical.
Never heard of this guy? When do the ring leaders get prosecuted, I bet never.