Nothing .. I was wrong. Switching only wins when Monty avoids opening the car door. If Monty opens a random door, then switching makes no difference. The flaw

Nothing .. I was wrong. Switching only wins when Monty avoids opening the car door. If Monty opens a random door, then switching makes no difference. The flaw in my logic above for the random case is that it's 1/3 chance orig pick was right, 1/3 chance unopened door, plus 1/3 chance that Monty opened the door with the car behind meaning you never even got a choice to switch.