Well,I've read it all. My thoughts:
Entry to the manoeuvre has been demonstrated to be outside of normal parameters. This includes busting the base height of 500ft.
Some possible technical issues (engine RPM and altimeter). Note that the possible altimeter error would have displayed a value lower than actual. There's also evidence that the pilot had altered thrust demand during the loop manoeuvre during previous displays.
Continuing the loop from an apex of 2700ft was unachievable.
More interestingly and probable far more wide-reaching:
Questionable DA/DAE procedures/process.
Maintenance and maintenance (regulatory) oversight was lacking.
Lack of understanding about who owned the 'risk' at air displays.
Poor, occasionally non-existent, safety management at many levels.
Summing-up my initial, most worrisome, thoughts in a sentence - The air display scene lacked effective oversight and suffered from ingrained and institutionalised denial.
AH may have pulled the trigger, but the system both manufactured and gave him the gun.