I see what you are saying, they never are directly over the cars in the (edited) video. However I feel this misses the point! The intent is clearly to "dive" the bridge by getting as close to it as possible, this could have so easily have gone horribly wrong. What happens when they make a mistake or a prop flies off?
The fact of the matter is you don't get to take risks with other people's safety. If the chance they hit a car is really only 1/100, then eventually someone somewhere is going to hit a car "diving" a bridge. It is hardly relevant that cars are more dangerous than drones... you still can't fly drones over people!