From all reports he trained his back hard just didn't have the genetics there.
That must be torture to have almost perfect genetics for bodybuilding except one big part like back.
No more so Than say a national level bodybuilder having the Grit/ Determination/ Mental attitude & train real hard & consistent year after year & not get anywhere near the size or physique Gary had, that's the Genetic lottery.
It would be much worse because he knows he was so close but one body part kept him from the top of the mountain.