Why do you assume he is listening to (or even seeking) advice before acting? Sure, being surrounded by “yes men” could be a problem, but its very hard from the outside to distinguish that from just being impulsive and not seeking input on the first place.
The observable difference I'd expect to see is that an impulsive guy not surrounded by "yes men" will still periodically commit avoidable errors, but not engage in a sequence of related blunders because someone will bring it home to him that things are moving in a bad direction.
