Most New Yorkers won’t get involved in anything.
That’s just not true. New Yorkers foil crimes every day - you just never hear about it. It’s not news. Also, watch NYers come to the aid of someone who takes a bad fall in the city streets; or watch strangers helping old ladies across icy streets in winter. I don’t know the full story of this particular case - and you don’t either.
I live in NYC and ride the subway every day. Your assertion that “most New Yorkers won’t get involved with anything” is untrue. In public places, whether in a park or on a subway, individual New Yorkers always align this way: good guys versus bad guys. I’ve witnessed crimes and have helped victims — I was one of many at one scene who helped — and my own life was saved by a stranger who intervened when I was mugged.
The fact is that the subway platforms are crowded and, even when they are relatively uncrowded, it is difficult to see what is happening more than a few feet away from you because the platforms are narrow. It is possible that the few people who witnessed this woman push the guy onto the tracks were too stunned to react. As for all the others who supposedly chose not to stop the fleeing woman: unless they actually saw her push the guy onto the tracks, they would not know why she was running away. If I saw a twentysomething woman of any race running quickly out of a subway, I would not tackle her if I had no idea what was going on. For all I knew, she could be running away from a criminal!
Let’s focus the blame in this case where it belongs: on the woman who pushed the guy onto the tracks.