Da kann nur spekulieren.
Er wartete wie üblich an, dass zunächst die anderen Besatzungsmitglieder ausgestiegen sind und hält das Flugzeug stabil. Danach war er vielleicht zu niedrig.Oder Splitterwirkung in den Fallschirm, etc.
Hier ein Beispiel, aus Bomber Command - Reflections of War, Band 4:
"It was clear that far greater damage had been done to the Lancaster than had at first been thought. The altimeter showed that they were now down to 2,500 feet. They would never reach the enemy coast, let alone their base. There was only one solution. Fogaty called up his crew and told them to bail out. Ferris was the first to go. From the rear-turret Sergeant E A Banham shouted that he was stuck. Pilot Officer Jock Simpson the mid- upper gunner scrambled from his turret to go to Banham’s assistance and made his way along the fuselage as the Lancaster skidded and lurched on its ever-quickening downwards course. Reaching the rearturret, he began to turn it manually so that Banham could escape and was rewarded with the thumbs-up sign from the rear-gunner, who then tumbled into space. Simpson slipped on his own parachute, informed Fogaty that the rear-gunner had safely bailed out and then made his own exit. Flying Officer P H Paddon the navigator and Sergeant ‘Jack’ Lomas the wireless operator followed him. Only Fogaty and Dams were left. Fogaty glanced at the altimeter and saw that they were down to 1,000 feet. If they were going to jump at all, it would have to be now. He unfastened his safety harness and motioned to Dams to hand him his parachute. Dams was waving his arms and pointing under the pilot’s seat, indicating that his own parachute had become jammed under the seat by their earlier evasive action."
feif: