A crumple zone reduces the force on the occupants because the same change in momentum is spread over a longer time.

True

True. The impulse $F\Delta t = \Delta p$ is fixed by the collision, so lengthening $\Delta t$ lowers F proportionally. Doubling the stopping time halves the peak force. Airbags, seatbelt pretensioners and the crumple zone all buy time rather than absorbing energy in the way the word 'cushion' suggests.