For years we wondered what Conqueror’s Haki’s worth was. Is it really just a fodder control technique? Now we see how dangerous this Haki is, and Luffy now realizes what he really needed to learn in order to beat Kaido.
Hyogoro’s bewilderment back in Udon. What Luffy did can now be explained.
Hyogoro is an Armament Haki expert, but since he does not possess Conqueror’s Haki, and the fact Conqueror’s can’t really be trained, it’s understandable why he couldn’t fully grasp what Luffy was doing.
This does make sense, as Conqueror’s Haki grows as the individual grows, even if they aren’t aware of it. Luffy, after his grueling fights in Enies Lobby and Thriller Bark, exuded minor Conqueror’s against Duval’s pet and scared it.
He then knocks out a few Amazons after his experiences in Sabaody and in a more stressful situation.
After his ordeal in Impel Down, he was able to effect an even larger radius when Ace was about to be executed.
After the timeskip, he now has control of it, and is capable of knocking out 50,000 Fish-Men, and tame animals with it.
In Wano, after his fights on Dressrosa and Whole Cake Island, he is able to use Conqueror’s Haki subconsciously, even using it after being knocked out by Kaido.
As Rayleigh said:
Luffy has never stopped putting himself in dire situations, and he has continuously met them head on. This has allowed his Conqueror’s Haki to become stronger passively along the way. He just had to know exactly what he was doing. He suspected it was the same as Armament Haki due to the visual similarities of what Rayleigh and others were doing, but in reality, he was referring to Conqueror’s.
Luffy is now facing Kaido as a great pirate. More than anywhere else in the story, he is exuding Pirate King energy. And thus Luffy’s quest to damage Kaido without damaging him is complete. His decisive battle has started, and I expect minimal interference from below outside of Yamato, who has loose ends to meet with their father, and possibly Zoro.