Yeah, its dangerous business pulling g's at low altitude. Not only does a pilots mind have to be in tip-top shape, but so does his body. Who knows why a highly experienced pilot went unconscious while pulling g's when a thousand times before he didn't? Perhaps he was fighting a cold, or got a poor nights sleep, or was even a bit dehydrated.
The Blue Angels trim their planes down, so a constant back pressure must be maintained on the stick. Lose consciousness and let got of the stick, and your plane goes down.