The Bystander Effect: why people in groups suck
It's easier not to take the blame if you are in larger group when something bad happens.
There were some explanations and theories about this in social psychology (which is very interesting by the way).
The other thing is that maybe people "freeze" by unexpected situation?
And thinking about MBTI types: maybe there is no action oriented Se funciton dominant people in the group to act: the ESTP's!