Why would the DoJ share that someone had a medical problem? People could become sympathetic. Better to focus the public interest on the greed and abuse of office aspects.
I read a lot of legal filings in criminal cases, and while you make a valid point my experience is the feds usually include whatever excuse/explanation people offer when they're caught. Culturally federally investigators more about 'here are the facts and how we collected them to establish probable cause' and leave the moralizing to prosecutors.
Please don't read this as a blanket endorsement or suggestion that federal investigators are always ethical, I don't believe that to be so.
