[Gunrunner2]

Just looked at the video.
Wow.
Hi-G turn, followed by a nosedive and an almost gentle nosedive, resulting in an attitude that the pilot HAD to know couldn't be recovered from (such a low altitude). My initial uninformed comment. . .I think G-LOC ("black out") and the jet went in. No mechanical malfunction.
Now, to be sure I'd like to know his exact planned flight profile before I can make a more forceful determination.

[RicocheT]

The pilot ejected, so no black out. Probably engine stall and too steep and angle to recover. You can't overfly the crowd on airshows as a crash endangers the spectators.

[b4its2late]

If the pilot B'dout, how could he have ejected? Does the co-pilot have a control to set them both through the canope?