I think you're underrating Smith's skills and overrating his power here. He's not a particularly technical fighter but he does most of the fundamental stuff right, keeps his guard up, boxes behind the jab, doesn't recklessly wade in or wing crazy shots from out of leftfield (much). His strengths are his ability to close fighters down and throw punches in bunches without smothering his own work, and to generally make things really rough and awkward for anyone that can't keep him off them. Sooner or later the cumulative effect of that sort of assault is going to break fighters down, which is what we see in a lot of his fights. It's not a case of him being soundly outboxed round after round then landing one shot and knocking his opponent unconscious. There's generally a grinding pattern to his fights where multiple punches have already landed before his opponent drops. Contrast that to Wilder who truly does just get by on just his power, and frequently finds himself at a massive weight disadvantage to his opponents, and I don't think Smith's in the running here. Hard puncher no doubt, but there's more to his game than you're seeing.
Wilder for a Heavyweight has tremendous speed and quick twitch. And also the best stamina in the division among the upper echelon.
And like, the thing is, Joe doesn't even make the slightest effort to box, he just comes forward, plants, badly telegraphs, and launches murderous power-only punches. Kill or be killed. Hes taking you out or you're taking him out. Respek.
Because he has the speed to apply the power out of nowhere and the stamina to be dangerous for 12 rounds. The point is Wilder doesn't have just power going for him, which is what you asserted, and I dispute that. That is the point.
There is no effort to do anything, but walk directly towards you and throw a punch as hard as possible.
Take your Joe Smith loving ass out of here. I like Joe, but he isn't pfp the hardest puncher by far. All he did was knock a 50 year old man through the ropes that you all hated, and Hop wasn't even hurt. He punches hard only if you let him.
Smith also has great stamina to be able to keep up a constant high workrate round after round. And his fundamental skills are a lot better than Wilder's, who still makes massive rookie mistakes. You're right, neither fighter just has power going for them, but Wilder is a lot closer to that statement than Smith.
I think part of the key to Wilders stamina is he is economical in his approach. He is not dancing and throwing a lot of punches. Not every one of the punches he throws is with bad intentions. When he sees his opening though. BAM! It's that economical approach and the fact he's light by modern heavyweight standards that contributes to his endurance. He is always seemingly in shape too which is something you cant say about all other heavyweights. His training camps do not need to be "fat camps" or "weight watchers clinics". Yeah he is limited as a boxer but he seems to "want it" and keeps himself in fighting shape.