Brain Size to Body Size
When I took Driver’s Ed decades ago, I remember one of the lessons was that intelligence depends on the ratio of your brain size to your body size. Elephants’ brains might be much more massive than humans, but their bodies are even more massive, so elephants aren’t as intelligent as humans.
This was relevant to driving because when you sit down in a driver’s seat, your “body” is suddenly multiples bigger than it was and you are comparatively dumber while driving than when you’re walking.
I’m not sure about the scientific backing, and it was more than likely just a way to tell dumb teenagers to be more careful, but there are other parallels. When a person makes a decision for a group of other people, their intelligence and judgment are similarly constrained. It’s harder for them to receive sensory input and circumstances are more unforeseen. Reaction times are slower.