It wasn't the DOJ IG, it was the DOE IG.
Note that some same people were involved in the 2015 case:
“The DOE-OIG and FBI investigated the case. Trial Attorneys Christopher Cestaro, Ephraim Wernick and Derek Ettinger of the Criminal Divisions Fraud Section and Assistant U.S. Attorneys David I. Salem and Michael T. Packard and Special Assistant U.S. Attorney Meghan A. Leibold of the District of Maryland prosecuted the case.”
Condrey is still awaiting sentencing after 2.5 years. Can mean only one thing; he's cooperating with the feds.