I really do wonder what Kuzan’s goal is.
Does he just want to reach Laughtale and learn the truth of the government?
Does he want to take down the government?
It must be something anti world government because the point of letting Robin escape and grow up was to see if the government was actually correct in its dogma and I think we can infer the outcome.
TLDR: Kuzan accepted the One Piece will be found, a giant war will happen, that the Marines can't stop Blackbeard because he twists their own rules against, and that Blackbeard needs to be taken down from the inside. Kuzan quit after Marineford because he realized the Whitebeard Pirates were the good guys, not the Marines, and that the freedom of piracy allows for some justice that can't exist in the Marines.
Kuzan and Garp mirror Shanks and Roger; Shanks wants to honor Roger's legacy by helping Luffy be Pirate King, while Kuzan wanted to stop another Pirate King from existing.
Now that Kuzan realizes the One Piece will be found, he's decided to join the Blackbeard Pirates, because Blackbeard is the worst pirate who could find the One Piece. Kuzan will end up betraying Blackbeard to help Luffy become King of the Pirates, because Kuzan knows through Garp, Robin, and Marineford that Luffy is the best pirate possible to become Pirate King, and that Teach would throw the world into chaos.
Full Post:
At first, Kuzan wanted to be like Garp, and practiced "Burning Justice". Once Ohara literally burned all around him, and Kuzan saw how much suffering could come from "justice", he switched to "Lazy Justice".
While practicing Burning Justice, he tolerated mass murder, and, then, under Lazy Justice, he allowed Robin to escape, run loose, and gave the Straw Hats a chance to save her from CP9 after letting her escape a second time, before finally letting her go completely a third time.
So, the question is, what justice did Kuzan come to after Marineford to change him this much? To me, Kuzan is a realist. Once he experienced Ohara, he stopped directly hunting down people who researched the Void Century, because he realized it wasn't congruent to his sense of justice.
Marineford was supposed to be about bringing peace to the world; kill the son of Roger, defeat the Whitebeard Pirates. What actually happened? Blackbeard replaced Whitebeard as a Yonkou, and Whitebeard's territory either was ravaged by Blackbeard or other pirates, with many innocents dying as a result. The Marines lost so many men, and gained nothing. Whitebeard was shown in Oden's flashback to openly run away from Marine forces if given the chance, and Whitebeard had no interest in the One Piece himself; he was a threat to the Marines in title only.
Akainu wanted to destroy Whitebeard no matter the consequences to the world itself, purely because Whitebeard was a pirate. After Whitebeard's death, and Blackbeard's take over, Kuzan was forced to accept that Ace's execution was a mistake. The Pirates had been the good guys, not the Marines. The Marines winning had made the world a worst place, not a better one.
I think Kuzan learned two things from Marineford:
1. Pirates are capable of doing good that Marines aren't capable of doing, because Pirates are not bound by the law.
2. Whitebeard was right; someone WILL find the One Piece, and WILL trigger the Final War for the world itself than Doflamingo keeps bringing up. There is NO ability to stop the One Piece from being found and that war from being fought. It's fate.
So, Kuzan decided he'd either take over the Marines and reform them himself, or, if he failed to beat Akainu, work on the Pirate side to handle the One Piece being discovered.
Many people view Shanks as Roger's gatekeeper, a Yonkou keeping other pirates from reaching Laugh Tale. I think Kuzan is the same, but from Garp's perspective.
Roger wanted to find the One Piece, Garp wanted to keep people from hunting it. Shanks wants Luffy to find the One Piece, Kuzan didn't. BUT, the difference between Garp and Kuzan, is that Kuzan HAS ACCEPTED the One Piece will be found. So, if Kuzan didn't want anyone to find the One Piece, because he was scared of what would come after, but had to accept it would be found, what's the most logical course of action?
Prevent the worst candidates for the One Piece from claiming it.
Who is the worst possible Pirate who could realistically claim the One Piece, the most vile, disgusting pirate who breaks all the rules, and murdered his own crewmate, then former Captain???
I lied; Kuzan learned a third and fourth lesson from Marineford.
3. The Marines cannot stop Teach, because he twists their own rules against them. Blackbeard can only be stopped by people who don't play by the rules (pirates).
4. The person who should be King of the Pirates is Monkey D. Luffy.
Kuzan already has a natural affection towards Luffy due to Garp and Luffy's treatment of Robin. In Marineford, Kuzan witnessed Luffy fight against all odds to save Ace from the execution stand.
To Kuzan, Luffy is by far the best option available if the One Piece is going to eventually be found.
Burning Justice is now Icy/Ice-Cold Justice. If Kuzan has to become a pirate, and do horrible things, to stop Teach when it matters most... he'll do so. The greatest threat to the world is Blackbeard claiming the One Piece, so Kuzan, a Hero of Justice, will do everything he can to stop that from happening.
THE GOAT