Churchill also had a horrible issue with deciding something on a whim, becoming attached to it and not letting go. See Gallipoli, Norway, Greece, Second BEF, Italy... and those are just the ones he succeeded in forcing through. Alan Brooke apparently was fighting a second war in Churchill's bunker throughout the conflict shooting down bad ideas sometimes at length because Churchill refused to let go.
Then there were the political misjudgements unrelated to the war such as the gold standard and India.
I think that IQ is a very poor way to judge intelligence beyond the theoretical.