I cannot claim any particular expertise, and certainly not in aerobatics in high-performance jet aeroplanes, but I do have some experience of "congnitive impairment".
Most of the posts I have read on here from obviously very experienced fast jet pilots (current or former) seem to be "locked into" discussion of impairment due to various stages of G-LOC. But when AH commenced his loop he did so from level flight, at 1G. This is reported to have been already far too low and too slow.
The AAIB report then states that there were random throttle movements, instead of immediate application of full throttle.
Then, arriving at the top of a loop (which had become 'bent') an opportunity to escape from being too low and too slow was missed. On the way down it must have been obvious to the pilot that he was going to crash, yet he didn't turn away from the road, nor attempt to eject and save himself.
It seems to me, therefore, that there was a degree of impairment from the begining and throughout the manoeuvre, which was NOT G induced.
One condition that can cause this is a Transient Ischemic Attack (TIA) - sometimes called a 'mini-stroke'. When this happens, an individual can appear normal, and may make seemingly deliberate actions, even converse, but be unable to realise what is going on around them.
A TIA can happen to anyone, at any time, and can leave no detectable physical trace. Sometimes it can happen again, sometimes it can be followed by a full stroke or even death, and sometimes by nothing at all.
That AH survived at all is nothing short of miraculous, but the whole desperately sad and tragic event resulting in the loss of so many lives may not be anyone's "fault".