Fires like this were easy to start. With so many different flammables on board from fuel, oil, hydraulic fluid, insulation etc, and pressurised oxygen, it wouldn't take much to get a fire going, and once alight, they burn very fast.
With so much of the forward fuselage destroyed, I suspect that repairs involved replacement of the front fuselage sub-section from the nose to the rear bulkhead of the radio room at the aft of the wing. There was bound to be a "Hangar Queen" on base to use for the donor fuselage.
Many aerial and ground photos of airbase technical site/hangar areas, show several "Hangar Queens" missing major sub-assemblies. Parts shortage was a major problem for the 8th AF, especially in the first 18 months operation. Ground crews learned to strip badly damaged aircraft for parts to keep the others flying, and some learned to "Midnight Requisition" extra supplies and hide them away in local farmers barns by a mutual arrangement.
When B-17G "Hang The Expense" crashed into the barn at Thorpe Abbotts, none of the investigating officers and wrecking crew thought to look in the other end of the barn. Fortunately, the undamaged and undiscovered end was the secret parts store for Bill Carleton, 351st Squadron Engineering Officer. He learned early on in the war that running a B-17 Squadron was going to take more parts than the officials allowed for. Changing the paperwork to allow more parts, would take longer than the war would last, and so "Midnight Requisitioning" of parts was the order of the day with the surplus hidden away.
Steve