If he were a real patriot he would have resigned before the election and let the chips fall where they may.
Good point. It suggests that maybe they finally came to a point where they agreed to disagree, but that Petraeus may have agreed to keep quiet about it, in return for getting his retirement benefits without any trouble.
On the other hand, i's traditional for cabinet members to offer their resignations right after a re-election. Sometimes the whole cabinet has been asked to submit resignations, so the Prez can decide which ones to keep on and which ones to let go. Maybe that's what happened. Although in Petraeus's case there were certainly special circumstances--especially the forthcoming grilling by the Senate.