captanzuelo
Member
This type of damage to the seat usually occurs when there's an occupant. The chair back breaks with the load of the passenger pressing back on it during impact. It should not happen and is very dangerous to the occupant as the seat completely fails to protect you. Based on how it is twisted as it broke, it is very likely that the occupant suffered spinal injury. There are many product liability lawsuits for defects such as this.
Perhaps it has to do with the chair mounts being placed on stilts, for all intents and purposes. Higher up, and away from the frame would create more leverage from the frame pushing forward in a rear impact. Factor in a heavyset person(just speculating in this case), and maybe the force was just too great.