Warning! Spoilers for Jujutsu Kaisen Chapter 191
If Jujutsu Kaisen's Kenjaku has had his plan set in motion since the beginning, the series' heroes have accidentally been helping him evolve humanity using cursed energy to usher in a Jujutsu Golden Age. Chapter 191 suggests that Kenjaku has controlled the Jujutsu Headquarters since the end of the Shibuya Incident, although details imply his influence was long before the manga's events.
During the Shibuya Incident, the world of jujutsu sorcerers was shocked after Jujutsu Kaisen's most powerful sorcerer, Satoru Gojo, was sealed in the Prison Realm. Jujutsu Headquarters saved itself in the aftermath by branding Gojo as an accomplice in the Incident and exiling him from the Jujutsu world. Furthermore, if anyone tried to remove the seal and release Gojo, they would be considered a criminal, while Gojo was set to be executed if released from the Prison Realm. Additionally, Yuji Itadori's execution is to be carried out immediately by Special Grade Sorcerer Yuta Okkotsu. While Yuji and the others risk their lives in the Culling Game to free Gojo, Noritoshi Kamo returns to the Kamo household to plead with one of the most trustworthy and influential members, Gajukanji, to have Headquarters' notice revoked. Working from the shadows, Kenjaku continues to penetrate the ruling bodies of the Jujutsu world to make their decisions go according to his plan. In doing so, the manga implies that it centers around Kenjaku's story instead of Yuji Itadori.
Chapter 191 opens with a flashback where Kenjaku confronts Noritoshi at the Kamo household. Due to the recent events that have shaken Jujutsu Kaisen's world, Noritoshi believed that if the main antagonist is a Kamo family member, then the conservatives in Jujutsu Headquarters were already manipulated by Kenjaku. Kenjaku reminds Noritoshi that he looks like Sugoru Geto, who Gojo executed, so only some conservatives were corrupted due to others' belief that Geto was still dead. The conservatives who do not believe in "Geto" can be convinced to change their minds on the notice, according to Noritsohi. Unfortunately, Kenjaku has already taken control of headquarters and murdered those who were suspicious enough about Geto that they ordered his execution. He also murdered those who wanted Yuta Okkotsu to execute Yuji Itadori, suggesting Yuji or Sukuna are essential to Kenjaku's plan.
Kenjaku's manipulation since the Shibuya Arc led Maki to slaughter the Zenin clan, Hakari to join Yuji and Megumi's team in the Culling Game, and Principal Yaga's death. Readers are shown this series of events to understand the gravity of Kenjaku's control over the Jujutsu world and how he is simultaneously influencing multiple main characters. By having Kenjaku lay out Noritoshi's plan and disrupting it, readers are shown how Kenjaku's actions add pressure on the heroes and bind their hands. Consequently, they have no choice but to play the Culling Game, the horrifyingly epic battle royale that Kenjaku created to kill weak sorcerers. Additionally, Chapter 143's revealed Yuji's father, Jin, arguing with his grandfather, when Yuji's mother interrupts, she has a scar across her forehead that closely resembles the scar on all of Kanjaku's possessed bodies. This flashback supports the theory that Kenjaku took control of another woman's body to produce a human-curse hybrid and would explain why Itadori can control Sukuna. Although Gege Akutami hasn't confirmed this connection, the detail about Yuji's mom implies that Kenjaku created Yuji so he could disrupt the jujutsu world by being another human-curse hybrid.
Even though he is not a member of the higher-ups at Jujutsu HQ following the Shibuya Incident, Kenjaku's influence on them and the Kamo clan has indirectly shaped the jujutsu world according to his goal. As a result, Jujutsu Kaisen's entire story follows the consequences of Kenjaku's actions and how they cause chaos throughout the whole jujutsu world.