Sorry MOR but most people finding themselves inverted or nearly so the first time will, at lowish level, (below 1000') spear straight into the ground. Pushing forward to keep the nose up is not a normal, instinctive response. It feels uncomfortable and unnatural so 'most' people wont push hard enough nor use top rudder to help roll rate and hold the nose up passing through wings verticle.
Below 500' no-one short of a trained aerobatic pilot will get away with it...and maybe not even then.
The quality of and the way 'most' pilots wear their seatbelts suggests to me they would be lucky to retain enough control to have any positive effect.
As far as this accident is concerned I don't think the fact he was alone is the kicker. Training and standards are the issue...plenty of people have logged many 1000s of hours SP IFR and lived.
Just plain stupid was probably the biggest contributing factor.