If you look at some of the other YouTube Videos, you'll see the aircraft did a zoom climb rolled and dived into the ground. It was clearly not under control from the start of the zoom climb.
I don't race aircraft, but I do race vintage cars - another sport where lots of old guys go to have fun.
Last weekend, there was a fatality at a vintage race at Watkins Glen - the car simply went straight on at full speed, whereas the track turned right. There was no attempt to turn the corner.
Increasingly, it is becoming clear that many accidents such as this are caused by the driver having a heart attack and simply not being in control of the car. That's what happened at the Glen, and that looks awfully like what happened at Reno with the Mustang.