Landing gear.
BoeingMEL,
I didn't see any pictures of the landing gear being down, only reference to it being (apparently) selected down.
But on most small Pipers the landing gear is held in the UP position by hydraulic pressure alone. No locks. Loss of Hyd pressure will cause the gear to freefall down.
During the break up the hyd lines will have failed causing loss of pressure and subsequent free fall of the gear.