Punching power has zero to do with arm strength....Lifting weights is a PUSHING motion...punching is a SNAPPING motion....a snap can't be built...Sorry, bro.
You can work out forever and have heavy hands, but you will never wreck a chin unless you have form or were born with K.O. power.
Iam no expert really on boxing ,martial arts etc etc, but surely bodyweight does matter to an extent with how much damage a punch does? But I do agree though, that some people can punch and others cannot. For instance at my local amusement arcade there is one of those punching machines, where you get a score for how hard you hit, of all my friends there, there were ten of them, I hit the hardest, and some were bigger than men,some could really fight as well.
In fact I hit so hard that day it attracted attention from some rather dodgy characters, who suddenly saw me as someone to fight especially when they challenged me on that machine offering up money and I won. , and the problem is I might be able to punch very hard,but Iam not a fighting man Iam soft , and there was a bit of trouble.
My granddad boxed nationally, while in the armed forces ,maybe it's genetic?