And remember, the part of the Pentagon that was hit was armored against such impacts. Which makes the hole smaller.
Indeed, and here (in De Bijlmer) the plane also hit a inside corner making the building a bit stronger and thicker then the rest of it.
Note that the debris behind the building is mostly of the building. Most of the plane never came through. The building simply “ate” it.
Also note that the filled up Boeing just left from Schiphol airport en route to Tel Aviv and only managed to lose about a third of his fuel above the IJsselmeer.
The pin of the engine that broke was the forward pin which was of the wrong type and old and worn out. This made the engine plunge down hanging on it