They stopped leaning right back and throwing punches from the moon, they threw tighter and turned their hip and feet when punching
Because one, technique, while it can contribute to power, is not the largest factor. Two, Saddler is not the sort of fighter who throws in the most efficient, power building way - his power comes from the exact same place Walcott's likely did, and that's God, not technique - and three, there's no footage of Barbados Joe Walcott, so how do we even know he has worse fundamentals than Saddler.
Walcott. He carried his power all the way up to heavyweight. Heavyweights were saying that he was one of the hardest punchers that they had been hit by!