I race cars and what I can see made things so much worse was that the car stationary on the track must of been in gear or the guy was on th brakes, if not, energy would have been dissipated into the second car causing it to move and therefore less damage to the moving car.
Donington is a terrible track if it’s raining, the water actually runs on to the track and the surface is very slippery which is why stationary car had spun and was stalled.