Sounds like pressing TOGA with an asymmetric engine speed, most likely caused by having one engine at a higher setting during the 180 degree turn at the node.
If #1 thrust had been used to help turn the aircraft while #2 stayed at idle, and then TOGA was pressed before allowing both engines to stabilise, you could easily lose control. #1 would accelerate much quicker to TO thrust, while #2 would have to accelerate from idle.
Never flown the 73, but I've ridden the jumpiest many times before. Those CFMs have a very long spool up time from idle. If the pilot was distracted or didn't get on top of it quickly enough, things can very quickly turn pear-shaped.