This is just getting so weird, if this is true. Apparently the original FBI agent who initiated the investigation was a friend of Kelley's. After
initial looks he forwarded the complaint to the Cyber Crimes division of the FBI. The agency felt he was becoming obsessed with the case and removed
him from it. There are also claims in the article that some "anonymous" source observed Kelley touch Petreaus suggestively under the table.
Also I read in another article also at Wapo that Petraeus was NOT going to resign because he thought that the affair would not become public.
It is a long article but worth the read.
Link
New details about how the Federal Bureau of Investigation handled the case suggest that even as the bureau delved into Mr. Petraeus's personal
life, the agency had to address questionable conduct by one of its own—including allegedly sending shirtless photos of himself to a woman involved
in the case.