Inverted spins are nasty.
Recognizing a spin onset and running the spin recovery procedure takes a decent amount of wits. Throwing in a reversal of one of the control inputs doesn't make it any easier...
Throttle--Idle
Rudder--opposite direction of spin
stick--forward
ailerons--neutral
flaps--up
rudder--neutral
recover from dive
Now, throw in the fact that the stick has to come back if you are inverted...and that you have serious G-forces...and a ton of stress...and limited time. Not a fun situation, especially when it's unexpected.
Add to that, there might have been a mechanical failure to initiate the spin, in the video.