The way I understood this thing with the A320 crash in France was that they were waiting for the protection offered by the Auto-Throttle System to kick in: 'Alpha Floor'. In the low speed/high AOA protection mode (the yellow/black band on the airspeed indicates that when we are entering this mode), the autopilot kicks off, nose up trim is inhibited, the max bank angle is reduced to 45 degrees. The side stick now controls AOA directly. Whe speed is reduced further, then, with an operable auto thrust system on the plane, the system will increase thrust to TOGA when this 'alpha floor' is reached.
I guess those guys were waiting for this automatic protection to kick in (for demo purposes) but nothing happened. Why?? It is disabled below 100' RA not to accidentally add TOGA thrust when you're about to land the plane and have gotten a bit slow during the flare. Wouldn't it have been in the landing configuration, the thrust would have kicked in. While they were waiting for this, the trees came closer and when they finally increased thrust manually, it was too late.
On the A319, by the way, this function is inhibited with single engine and Flaps/Slats in Config 1 or greater, I gues due to the limited rudder ability to counter the yaw at slower speeds with the shorter fuselage, even though the max deflection is 30 degrees instead of 20 on the A320.