While I agree that stopping and making sure things are okay would probably be the best thing, there's still a few concerns.

1) The power lines are a serious threat to anyone stepping near that crashed car. You have no guarantees that they won't snap, fall on and fry everyone in range at any time. Going to help the people in that car is a serious risk to your own life.

2) Someone speeding like this in a residential neighborhood (read above they were going near twice the speed limit) are also quite likely to be extremely aggressive and possibly violent. If they were physically fine inside the car and believed you just caused them to crash, there would a decent risk of violence when stepping out to help.