Yhwach approached Aizen and asked him to work for him as he destroyed Soul Society, referring to him as a “Special Threat.” Aizen graciously declined and even slightly altered Yhwach’s perception. Later, after being set free by Yhwach, he continued to refuse to go with him and aided Ichigo in killing the Quincy Emperor instead. Why? Aizen was a conceited Shinigami and a narcissist who desired to be the only one in control of “his” universe. Although it was motivated by self-interest, Aizen’s assistance was actually invaluable in this situation.
Why did Aizen help Ichigo against Yhwach?
We must briefly describe Aizen’s personality in order for you to comprehend his motivations. Aizen’s personality truly has two facets. Many people, especially his second-in-command, Momo Hinamori, adored Aizen at first because he gave off the impression of being a very amiable, well-respected Captain. He gained the respect and favor of the majority of Soul Society members by being consistently polite and respectful.
This was simply a cover to hide his true personality, which was extremely threatening and cold-blooded. In reality, he doesn’t give a damn about his subordinates (past or present), and he’s happy to use practically any of them as a tool in his own made-up game, “a chess game.” He claims that he is not constrained by any moral principles.
When several of Aizen’s subordinates—including Kaname Tsen—die in the battle of Fake Karakura Town, it is evident that they were merely tools for his purposes. In most cases, he chooses to ignore their deaths or dumps his “too weak” subordinates, claiming they are incapable of fighting for him. Aizen, however, appears to overestimate his abilities and has lost the habit of overanalyzing things when he is close to attaining his objective and endowed with extraordinary talents. He claims that nobody can now harm him.
The best way to describe Aizen’s behavior is as a rampage. Actually, he had already given up on trying to fit in with the crowd and instead wished to alter the course of the world. He had to depose the Soul King, who Urahara claimed to be the center of the spiritual universe, in order to accomplish this. Aizen presumably didn’t care if he made it or was stopped if someone had the authority to do so. It would have been the realization of a wish in both scenarios.
He was given much more potent abilities by the Hougyouku, though, therefore he was unable to acknowledge an equal as such. He also didn’t see how a human could be more powerful than a Hollow.
Aizen was ultimately a narcissist, but he did take pride in himself for being a Shinigami and believing that he was vastly better to everyone else. Aizen specifically believed that he was the series’ most strong character. Despite being aware of the weaknesses of other characters, he believed he could defeat or outsmart them all, which is why he actually headed for the Soul King, the deity of Kubo’s world. His narcissism ultimately caused him to fail, yet this is crucial information for comprehending his choices in the end.
How did Ichigo and Aizen defeat Yhwach?
Knowing Aizen’s strength during the Thousand-Year Blood War, Yhwach attempted to persuade the renegade Shinigami to join his cause, but Aizen flatly rejected. Later, Yhwach released him, but Aizen thanked him before turning against him. Aizen merely stated that he did not want anyone controlling him, not even Yhwach, in response to Yhwach’s questions about the action.
Renji and Ichigo attacked the Quincy Emperor while Aizen and Yhwach were conversing, which led to a fight between them. Now, this is when Aizen’s Kyka Suigetsu really shone, as it not only assisted in slightly weakening Yhwach but also provided Ichigo with the required opening to actually overpower and kill Yhwach.