He suffered a ‘G’ stall, where an aircraft stalls at a much higher speed than normal due to G forces. Air isn’t moving over the control surfaces and you’re basically fucked. You can anticipate this as the loss of control is progressive, but he had no reserve of thrust to counteract the effect. I understand the engine had been wheezing even at take-off, which should have meant throwing the whole display away and landing asap.
Military aircraft are not designed for hobby flying due to the demands of maintenance and associated logistics. Add to that the fact that it’s a jet, and you have issues of cumulative airframe stress. Some Russian privateers will take you to the edge of space in a Mig25 for £15,000 but I’d rather pour napalm down my urethra and call myself Guy.