i think hagler would have had far too much for him even when he was young champ i think he could have out boxed him on the back foot
Exactly. Hagler's lack of experience was the reason for his early losses, he simply hadn't come into his own, and was clearly pre-prime. By the time he won the title, he had hit his peak and was head and shoulders over most of the division, including the guys that had beaten him early on, and he proved it in dominant fashion in the rematches.