"The rope is supposed to be taught before the floor is dropped out...otherwise the hangman runs the risk of the rope breaking or the head popping off due to excess body weight...the goal is to strangle the man whilst breaking the neck..."

This is not the official video since that was taken from the top of the platform. This is a real video however. The rope is not supposed to be tight as this would strangle. In a proper hanging the knot is placed slightly to the side and back of the head with the slack calculated for proper drop based on the weight of the person being executed. Upon dropping the knot snaps straight and either (preferably both) assists in breaking the neck and/or knocking the person out. The fall and the knot both aid in breaking the neck leading to almost instant death. Only botched hangings strangle.