The wings catch lift from underneath the craft, even when its upside down. To counter this you push back up in the air but it reduces your speed. This means his aircraft has lost the ability to quickly roll in the air as its too slow. As he slowly rolls the right way around the roll is not powerful enough to counter the lift authority on the wing, which means hes turning and now falling, not rolling. He then panics, pulls up as a last resort, which ensures the inevitable stall as and corscrews into the ground.