I thought that was my Flight medical!Are you a current holder of a medical Marijuana card?
Seriously, it looks to me like the pilot did a nice little hammerhead, found himself pointing nose down lower than he was prepared for, and pulled too hard while also trying to stop the slow "roll" he was in. Not a snap, it looks like but a spin. Far too low & just as important, going down too fast to recover. I don't think he was in a spin until the hard pull up.
The video could be clearer, and I could be wrong. It is a tragedy every time someone messes up.
It's also possible that there was a control system failure, or a water bottle jammed under a rudder pedal, or in the stick mechanism, or...... But "hey bubba, watch this" seems to be the root cause.