[Serpiko]

Judging by images only, the maneuver was intended to display the ability of the plane to reach a high angle of attack. Such maneuver actually brings the plane at the limits of controlled flight, therefore there's little or none margin for errors or failures. In that case, if you don't have enough sky below you...

Moreover, with such a low speed and high AoA, rudders and engine air intakes are likely to suffer a drop in efficiency. Even if these factors haven't been the cause of the crash, they probably concurred in preventing the pilot from recovering control.

Thank God nobody got hurt... when I see an arshow crash, my mind always goes to Rammstein tragedy.