Why Did Aokiji Join Blackbeard

Aokiji (real name Kuzan) joined Blackbeard’s crew following a series of disillusioning experiences with the World Government and the Marines, particularly after his clash with Akainu over the future of justice. His decision reflects a complex mix of personal values, strategic motives, and potentially hidden agendas.

1. Disillusionment with the World Government
Kuzan grew increasingly skeptical of the World Government's moral authority, especially after witnessing corruption and authoritarianism within its ranks. His sense of "lazy justice" clashed with the extreme absolutism of Akainu, who was promoted to Fleet Admiral after defeating Aokiji at Punk Hazard. Unable to serve under someone whose ideology he fundamentally opposed, Aokiji resigned from the Marines.

2. Desire for Autonomy
Rather than aligning with any formal institution, Aokiji sought the freedom to act on his own beliefs. By severing ties with the Marines, he freed himself from bureaucratic restrictions, allowing him to pursue justice on his own terms—even if it meant operating in the shadows of piracy.

3. Strategic Alliance or Undercover Mission?
While he appears to be a member of Blackbeard's crew, there’s credible speculation that Aokiji may be working undercover. His knowledge of Blackbeard’s operations and proximity to key events—like the abduction of Pudding and the clash at Hachinosu—hint that he might be gathering intelligence, possibly for the Revolutionary Army or another anti-World Government faction.

4. Protection of Nico Robin and the True History
Aokiji has shown a long-standing interest in Nico Robin’s safety, possibly due to his connection to Saul and Ohara’s destruction. Joining Blackbeard—who has targeted Poneglyph readers—could be a calculated move to shield Robin from becoming a pawn in the Yonko’s plans.

5. Gray Morality and Independent Justice
Kuzan’s alignment with Blackbeard doesn’t necessarily mean he shares the crew's values. It may reflect his pragmatic approach to justice in a world where rigid morality fails to account for nuance. He’s navigating a morally gray path, possibly aiming to influence or destabilize Blackbeard’s power from within.

Conclusion
Aokiji’s decision to join Blackbeard is layered and potentially deceptive. While it outwardly suggests defection, his deeper motives may involve a pursuit of justice that defies both the World Government and the pirate system. Whether spy, ally, or rogue force, Aokiji remains one of One Piece’s most unpredictable and compelling figures.