In the 12 seasons (Manning) made the playoffs he has 11 playoff losses (t-most ever), 5 playoff losses at home (all as the 1, 2, or 3 seed), a game-losing interception in the superbowl, and 8 one-and-dones (remember, out of a possible 12)?
What did you expect when the Broncos signed him? Predicting anything other than one and done from him would be awfully delusional. He makes terrible decisions in the clutch and more often than not loses the first game of the playoffs, even when he's the prohibitive favorite to win.
Those who do not know history.....