@Richard_Pearse is the (former) airshow pilot, not me.
I saw the same overall lack of aircraft energy in the routine and agree that density altitude was probably a factor. Compared to the routines of the airshow airplanes of the 1960s it was plenty high energy. Compared to what you expect to see these days from any model of Extra, it was noticeably weak.
Agree w an attempted Lomcovák - Wikipedia. Which has been loosely described as “Force the airplane to tumble, then hang on until it does something you recognize, then recover from that maneuver, whatever it turns out to be.” A bit of hyperbole, but not too far off.
Starting from a climbing series of snap-rolls as he did is a pretty common way to scrub off the speed and get the gyro forces built up then transition into the forward tumble. In this case the plane makes an awkward double-tumble with a negative G jerk in the middle that just feels wrong, does a sort of inverted half-turn spin, which burns up altitude, then the recovery starts. But by the time he’s got the nose pointed towards the velocity vector which is nearly vertical downwards, and is fully under control, there simply isn’t enough altitude to finish the recovery, nor speed to pull more Gs to tighten the turn radius enough. So the ground gets there before he achieves level flight.
He (probably) had the altitude and energy for the double-tumble, or the half-turn spin, but not both. I don’t think that was a deliberate attempt, it was just the way the airplane happened to flop around the sky that day. I will suggest that at higher density altitudes the inertial forces are the same, but the restorative aero-forces are less. And the flight controls are somewhat less effective. Such that a more violent maneuver than usual might be expected.
Bottom line IMO: He had the bad luck to have the uncontrolled part of the maneuver end up with a flat inverted spin/fall, meaning he had to turn 270 degrees in the vertical plane to achieve level upright flight. And due to falling in planform orientation, his actual speed was very low as he started the recovery. Low speed = low ability to pull Gs and turn in that vertical plane.
On a final re-watching I notice that just before the airplane disappears behind the parked plane in the foreground, an unexpected and unhelpful right roll develops. Perhaps an accelerated stall as he makes a last-ditch instinctive pull?
Bad news all around. And probably much more a matter of bad luck than bad skill.
I’ve told this story before, but when I was an FO I used to often fly with a Captain who’d been lead of a 3-ship Extra formation act that toured back in the 1990s / 2000s. Damn but this guy could fly. They had a lot of fun and were paid stupid-level money by their big corporate sponsor.
I asked him why he/they quit. His answer was simple. “You either quit after you’ve really scared yourself a few times, or you’ll keep doing it until you kill yourself.”
I’m not suggesting Coleman had gotten past that “not scared anymore” point since I don’t follow the airshow game at all and don’t know who the current big (or small) names are, but for sure it’s a story of luck running out. Which amounts to the same idea my Captain was talking about.