The video is sped up. He was moving VERY slowly. He stopped each time he felt a wheel starting to roll over the edge. The front of the car is the heavy end. Nobody in back. The drive train center of gravity is slightly ahead of the center line of the front axle.
Yep. If the back wheels had gone off the edge the van would have just been stuck there. The weight is too far forward for the van to rotate back and fall off the cliff.