The people here having nasty turns for the worst when turning downwind are confusing the alleged perils of that with the real effect, dependent on gross weight, of climbing or descending through a wind shear whether turning or not. A 'turn' within a moving mass of air will have no effect on KIAS.
This guy died because he ran out of airspeed, due to trying to mishandle the aircraft out of a situation caused by his poor planning. He flew through numerous holes in the cheese to get there, including the lack of supervision by the airshow management; after all it was only a planned circuit, landing, water taxi and takeoff/departure so what could possibly go wrong ?