What the hell does body weight have to do with punching? If it does then why mention Tyson ? He was barely a heavyweight.
Are you serious? Of course weight matters a lot, there are weight-divisions for a reason, do you think middleweights or light-heavyweights can punch as hard as full heavyweights/super-heavies?
Funny that you mention Tyson as an example of "weight doesn't matter", Tyson himself NEVER fought under 200lbs, even amateur, he was a NATURAL, thick, muscular HW, even if short... Tyson was around 215-220 in his prime, got even heavier after... Shavers wasn't, he fought under 200lbs and his median weight was barely over it, not 215lbs...
Ali, Frazier, Liston, and such all fought under 200lbs, they were not natural heavyweights like Tyson... The only one was Foreman, and still his median weight in the 70s was 217lbs, basically what most cruisers of today easily weigh after re-hydrating, he would be an extremely light competitor today, with not much chances... His late 80s, early 90s 230+lbs version would fare much better...
Tyson is also an anomaly, we'll probably never see again such a short but explosive HW, having such success in an era where huge, skilled heavies started to appear... Still he fell short in basically all his signature matches unfortunately... But to show his prowess as a puncher and ko-artist, only him and Wladimir Klitschko were able to spark many guys even being outweighed in 50%, or more, of their bouts... Other famous punchers are notoriously heavier than opponents stopped...