Arnold was a fat fuck when he went to Vince. Vince taught Arnold how to diet for shows. If it wasn't for Vince Arnold may have never beat Sergio. Vince made Arnie better than the soft foreigner with great arms when he came to the US.
It's not like someone else couldn't have told him how to diet you know, someone from all the gyms he trained in, of all the pros he trained with etc.
You make it sound like if Arnold hadn't met Vince who was apparently the one and only font of knowledge at the time he would have been spinning his big fat wheels to this very day shaking his big jowls and scratching his head while pondering the eternal riddle of dieting that he never learnt because Vince died and took the info to his grave.