If you're at >100 feet at any sort of decent speed in a fast jet if you apply power and pull back in any sort of meaningful way by the time you hit 30 degrees of pitch you'll already be well above 500 feet....
Well in my fast jet, I just try to fly straight and level. But if I as much as sneeze, I can easily climb 100'. By the look of the video evidence, by the time the accident a/c hits 30* nose up, I would estimate an altitude quite possibly approaching 1000'? I am led to believe this pitch attitude is the point (and therefor the altitude?) at which the aerobatic manoeuvre commenced? I doubt very much it's lost much energy at that point either?
The people saying this a/c was "flying too low" must be talking only of the end of the manoeuver. Because if my understanding is correct, it certainly wouldn't appear to be an accurate description of the entry
I would humbly suggest that insufficient 'pitch rate' in the early stages of the second half of the manoeuver is quite likely to provide a clue? At this point in time, if the reasons for that are indeed known, they certainly have not been made public.
Fertile ground for the self agrandist speculators!