when there is a delay

"Crowding on Mooreville’s subway frequently leads to delays, because it is difficult for passengers to exit from the train"

please see the above sentence.

can the exit difficulty for passenger causes the subway delay really?

As per my understanding , people get down from train and walk along the subway(underground road ...right ?) ....there should be no delay.

I am not sure whether i am thinking in the right direction.
I just asking a general knowledge question