From the evidence that we see in the photos, I think what might have happened was that the car got under the tires of the combine just as the operator of the combine slammed on the brakes - which meant that the combine didn't allow the car to finish working its way out from under the tires. The combine then just pushed/dragged the car, leaving the marks that we see, and leaving the towed header with less damage than it would have gotten if the combine operators hand't hit the brakes.