My guess is that he didn't need to be told. 0bama couldn't just get rid of him without some justification, so he called the FBI in and told them that Petraeus wasn't "playing ball", and they needed to find something on him. Unfortunately he conveniently obliged with an affair. Quite possibly Broadwell set him up.
...............Unfortunately he conveniently obliged with an affair. Quite possibly Broadwell set him up...............
Gen Petraeus was a very smart child, unfortunately so smart that he was able to skip kindergarten.
That’s when they teach young boys to keep your pee-pee in your pants!