Maybe the FBI had the goods on Carter Page and forced him into an "undercover" position ...
Was Page a minor 'bad guy' who the FBI used as undercover in exchange for not arresting him? Then his 'good guy' exterior would be covering an opportunist a 'bad guy'? That would explain the mixed feeling about the guy. He wasn't originally on the side of 'good' he was reluctantly recruited?
Think a small time con artist who when caught either goes to jail or wears a wire when talking with the mob... or in this case the S.V.R. Foreign Intelligence Service (Russia)
It will be interesting to see what explanation Shiff and company will propose. Another story would be that Page was an FBI spy who became a double agent later on, or he was a double agent all along, and maybe the FBI didn't know it until later.