The thing is we don't know but they may have already unloaded a dozen or more flat cars exactly the same way without incident. This may have even been a case of laxation of procedural protocol due in part of the ease of off loading several cars previously. Or one operator could have sneezed causing him to jerk a lever or step on the gas but what ever the reason there still no getting around the limited safety factor of possible overloading calculated for the pick.