- Rayleigh has nothing more as a leader over Zoro , he was literally a chilling citizen that wouldn't even be a fighter without Roger or did we forget that ?
- Boa Hancock was literally a slave , no leadership ambitions til she got strong enough to be put as Kuja captain
- Kozuki Oden , literally the most anti-king conqueror haki user where he refused multiple leader positions always carefree
- Edward Newgate , chose to not be the Pirate King cause he doesn't give a fuck about it want to just be a father and sail the sea carefree
- Charlotte Katakuri not a captain and never shown the ambition to be one and just be a support to his mother
- Portgas D. Ace not a captain and just want to be a support to his father
I like how you call Usopp "accidental" even tho it's proven over and over that when it matter the most Usopp shows up that's his whole character and ambition to be a brave warrior of the sea
-Boa, leader/queen of Amazon Lily, her people admires and idealize her.
-Oden, the same as Boa. He is a natural king. Without wanting it, he attracts people to him. That's the point of a Conqueror user ability, he does not need to attract them or do anything, it's something natural.
-WB, same. One only needs to see the amount of Captains from the New World he gathered and followed him for saving a single life.
-Ace, basically a MC, that's why Oda killed him. And how not a Captain? He was a Captain until he joined WB. The same with the people in Rocks lol. And there is his bloodline -> Garp implied that Conqueror has a great chance to be inherited.
-Katakuri, the most outstanding child of BM, a Conqueror Haki user -> the same thing about inheriting it and probably he will be going to be a leader Captain in the future seeing how he developed his character in WCI.
Yeah, for now he is quite lacking comparing to others in that aspect.
-Rayleigh, explained before. He only has it because Luffy needed to be taught about all three types of Haki since he is a Conqueror Haki user, and there was Rayleigh. Aside from that, Rayleigh has nothing to do with a Conqueror Haki user for what we saw about him. So plot reasons.