Take and punch a wall/something solid with your fist. This is how cars used to be. The same energy at the bumper at impact was imparted to the passengers.
Now put on a boxing/sparring glove or put a piece of foam on the object and then punch it again. This is how cars are designed today. The speed is the same. The energy at the point of impact is the same. But, the energy of the impact at the bumper is not the energy felt by the passengers.