Too much speculation
I really do have a problem with drawing conclusions from the rather odd video, not unusual with amateur takes, but I would like to wait until either Andy, do not know him directly but friends do, is able to say what the hell happened or it has to descend into conjecture.
I personally do not think a loop was the intention, possibly an Immelman, Andy has always been a good display pilot but never seen him endanger himself let alone others.
A terrible tragedy, but just why, need more evidence and there is not enough but that descent simply does not look right, I question if he had much control from the apex and tried to recover too late.
In other words I do wonder if he was not incapacitated at the apex - been there, done that, but with more air underneath.
I only have rather vague memories of the Hunter but I do recall it was very forgiving and everything about Andy says he would not go feral, so I do suspect he was for whatever reason struggling with consciousness.
Horrible, I don't have anything else to say really other than RIP to the dead.
Cheers