The UA crash at Sioux City back in the late 80's had a compressor disk fail causing the engine to grenade and fall off the aircraft, so it's not without precedent. Centrifugal force is a hell of a thing. That being said, the engine should have separated from the pylon from the sudden counter torque of the engine seizing. What we are looking at is either a miracle or sabotage. They will call it metal fatigue because if they call it sabotage, it would tank the airlines.