In the second one, you can just barely see right before it disintegrates that the plane is put into a bank and then rudder is applied. It looks like an "airshow pass", where it is banked and rudder is used to hold the nose up, like you would do for a knife-edge pass. It looks like the vertical stab ripped off from the stress of the full rudder application, and then the plane came apart from the aero loads from flying sideways.
Kind of like that airliner crash where the pilot applied full rudder during turbulence and ripped off the tail.
It looks to me like the airframe was too lightly built for anything but symmetrical loading and coordinated flight with very low sideslip angles.
