You know our country is in trouble…

People are conditioned to keep their mouths shut and head down on the subway. Also, as that video even tagged, did the person have a weapon? Most people aren't fighters.

And when he slams her against the door, that's when the rest of the train really noticed, but the video ends. The bigger guy in the blue shirt seemed to look back like 'what just happened.'

Before that, except for the few close by, the physical action is subtle.