Rain, low ceiling and temperature too close to freezing. Icing conditions and therefore they could not fly.
That spot is very safe, with a significant ditch, also we take the tape further up the hill in the runoff zone. Like tirc said, most people are standing well above the cars, except those that like to eat gravel. The area that the cars are coming from, in the video, slows them significantly as they have to make a 90 right on to a one lane bridge and then a 90 left up a steep hill.