The forward elevator on the Essex-class carrier was particularly important during the launch portion of its operating cycle. If an airplane experienced a mechanical failure as it approached or was on the catapult, it was probably the least disruptive way of getting the "dud" out of the way of the airplanes behind it waiting to be launched. Maintaining the launch schedule was critical, because much of a delay might impact the timing of the recovery of airplanes in the air from the previous launch. The elevator was originally 44-feet wide and 58-feet long. When down, it opened into the forward end of the hangar bay.
As part of the SCB (Ship Characteristics Board) 125 change to add the angled deck to Essex-class carriers in the mid-1950s, some ships received an enlarged forward elevator, with a triangular section was added to its forward end to make it 70 feet long. It isn't clear why this change was made. The elevator was still too small, both in width and length, for the Douglas A3D Skywarrior, which had to be moved to and from the hangar on the deck edge elevators. The next longest carrier-based airplane was the McDonnell F3H Demon at 59 feet, which was awkward to position on the 58-foot elevator, but did not require a 70-foot one.
My guess is that the extension on the elevator allowed a tractor and tow bar attached to the dud to all be accommodated on it. The dud could then be quickly towed onto the elevator, lowered with the tractor still attached to the hangar deck level, and pushed into the hangar so the elevator could be raised back up to the flight deck as quickly as possible and the launch resumed. This eliminated the time required to detach the tractor before the elevator was lowered and then reattach the dud to another tractor when it got down to the hangar deck so it could be pulled off the elevator.