Why is Wilder the Hardest Puncher at Heavy weight?

I've watched wilder KO fighters with that right hand but i have to ask where does he get his HUGE power from? Look at Wladimir Kilitschko, Punch technique is excellent, Huge Shoulders, Huge legs and Huge calf muscles. All these combined give him great power in his punches. But when you look at Deontay Wilder, he has Huge Shoulders, but he has really skinny legs and decent punching technique for a PRO (he windmills sometimes). So how does he generate so much power in his shots? Can he do this just by using his Huge shoulders to help turn into his right hand even without having huge legs to drive into his punches. Or are Wilder's skinny legs deceiving and are actually much stronger than they look without being HUGE. Although i have noticed that even though wilder has skinny legs, his legs are lean and move pretty fast as he is punching. Is this Why? Most big punchers had Huge Legs/ Huge Calves and Huge Shoulders e.g. Pacquiao, Golovkin, Stevenson, Mathysee, Tyson, Foreman, the Russian guy (forgot his name) who KO'ed Cleverly didnt have HUGE legs but you could see his legs were really solid almost like tree trunks.