A key moment of Eren’s rebellion involved him beating up Armin and escaping from his jell cell. But why does Eren beat up Armin?
Eren has to beat up Armin to push him away. He wanted Armin to hunt him down and be seen as a hero by the surviving world. Siding with humanity instead of Paradis and stopping The Rumbling would make the Scouts respected.
Later, the chapter reveals that Eren had little free will in the decisions he made. Beating up Armin was also part of fulfilling a pre-determined path set by the Founder’s powers that he witnessed at the medal ceremony.
Specific Plot Behind Why Eren Decided to Beat Armin Up
In the final Attack on Titan chapter, Eren communicates through Paths a final conversation with Armin. The two are speaking as their childhood selves, sitting on the same Shiganshina cobblestone wall where Armin brought Eren the book on the outside world.
The chapter begins in the middle of Eren detailing his logic to Armin. He says he understands Eren’s reasoning behind tirelessly fulfilling the future he saw with the Attack Titan’s powers,. Yet, he’s still upset that Eren beat him to a pulp to push him away.
“I was so desperate to push you all away, even I found myself wondering what I was doing. I just let the moment takeover, really. Sorry.”
Eren to Armin | Chapter #139
Armin realizes that Eren’s efforts were to push him and Mikasa away. It is also to make them heroes who saved humanity from extinction by hunting him down. Eren assures Armin that those who end The Rumbling will be seen as saviors by society’s survivors. They will also become the most respected people in the world by turning their backs on Paradis and siding with humanity.
Armin intelligently asks Eren if his plan involves them protecting Paradis from a potentially angered humanity outside of the walls. Eren assures him that outsiders cannot retaliate in their lifetime, as The Rumbling killed 80 percent of humanity.
“Did you really need to go this far,” Armin asked. “Was it really all for our sake?” This question posed by Armin is the first hint that Eren distanced himself for a reason greater than protecting his friends.
Eren Reveals The Founder’s Influence
After a discussion regarding Ymir and Mikasa, Eren continues to admit that motivations of the Founder continue to influence his actions. The future Eren saw at the medal ceremony was The Rumbling. This moment adds an unstoppable urge to walk that path and twist the world until that future is executed.
Eren’s reasoning for allowing the Founder’s Power to control his actions is insanity.
“Armin, my head’s…gotten all messed up. The Founder’s Power has made it so that there’s no past or future, it all exists at once.”
Eren to Armin | Chapter #139
Eren’s inability to rebel against The Founder’s powers’ will led to his final confession. He used the power to manipulate Dina’s titan to ignore Bertholt and walk towards Eren’s mother instead. It wasn’t Bertholt’s “time to die yet,” implying that Eren’s obession with adhering to the timeline of events pre-determined by the Founder’s Power is taken very seriously.
It is partly true that Eren beat up Armin to facilitate a situation where he can distance himself from the group and be hunted down. He was also ensuring that the timeline of events matched those pre-determined by the Founder in the medal ceremony.
The reason that Eren has to start The Rumbling is due to his obsession with following the pre-determined path he witnessed at the medal ceremony. The Founder’s powers have taken control of Eren and used him to manage the timeline.