This wasn't improper handling. Im 99% sure these TEST pilots purposely allowed a stall to happen to test how the aircraft would react. Thats why he keeps positive climb with dropping airspeed. If you notice the gimbal "shake" thats buffet and/or stick shaker indicating an imminent stall. The reason it rolled over is 1 wing stalled and the other didn't which is fairly common. What is even scarier is this airframe being a high tail and delta wing config can "super stall" where both wings do stall evenly and is un recoverable from what I understand. Dirty flowing air obstructs control surfaces and the pilot cant control attitude
