He brutally pushed Zeke toward becoming a Warrior candidate and infiltrating the Marleyan military. Grisha exclusively treated Zeke with this political aim in mind, never once concerning himself with the boy's well-being or whether he actually wanted a Titan stuffed inside him.
One thing is certain; young Grisha, who still resided in Marley, definitely didn't care much for Zeke. He even says so himself. But this is older Grisha speaking about his past self. He's criticizing his actions, and speaks with regret.
Why did Grisha give Eren the Attack Titan if he told Zeke to stop him?
Why did Grisha still give Eren the Attack and Founding Titans even though he knew what Eren's going to do? Part of it was that Eren was actually influencing events from the future. His future self was using his ability to affect the memories of past inheritors of the Attack Titan to influence his predecessors.
The weight of his ideals and his hardworking nature are such that he often neglects Zeke's well-being, refusing to spend time with him under the pretext of being too busy and continuously blaming him for his failures and pressuring him into becoming a warrior to save Eldia.
He was lonely and repeatedly mistreated and humiliated by his own father Grisha and by his then-chief overseer Magath, neglected by his mother Dina, mocked and singled out by his classmates for being weak, and hated and discriminated against by non-Eldian citizens for his blood.
The Story Of Grisha Yeager: THE TRUE RESTORATIONIST (Attack On Titan)
Why did Grisha treat Zeke badly?
He brutally pushed Zeke toward becoming a Warrior candidate and infiltrating the Marleyan military. Grisha exclusively treated Zeke with this political aim in mind, never once concerning himself with the boy's well-being or whether he actually wanted a Titan stuffed inside him.
However, Grisha explained that he believed the Marley men were lying and tried to say they killed his sister but Yeager silenced him and the two fought over their situation as Eldians.
It's also worth remembering Eren went from watching his mother Carla being eaten by a Titan - who later turned out to be Grisha's first wife Dina - to later being transformed into a giant and devouring his own father; that's a lot of therapy right there.
Grisha Jaeger - Dina met Grisha when he became a member of the Eldian Restorationists. She loved her husband unconditionally and, when they were sent to Paradis, promised that she would find him. Zeke Jaeger - As Zeke's mother, Dina clearly loved her son.
Witnessing his mother's death was traumatic enough, but seeing countless allies die in front of him was a major factor in Eren's fall to the dark side.
Why Eren and Zeke did not simply touch each other to engage the power of the Founding Titan when they met in the Liberio internment? If they did, Eren could have immediately had the power to manipulate the memories of all the Eldians people, including the enemy's intelligent titans (i.e. War Hammer, Jaw, Cart, Armor).
It's simple -- he is not of royal blood. In order to truly access the Founding Titan's abilities, the holder needs to be in physical contact with someone of royal blood. This is why Zeke Yeager is needed.
Eren's dramatic change in character came about after he kissed Historia's hand and saw the future, including a version of himself committing mass murder. All Titan Shifters in Attack on Titan have the ability to see the memories of those who held their Titan before them.
Despite believing he sent his father and mother to their deaths, Zeke sympathized with their goal to free the Eldian race. Thus, Zeke continued his parents' cause by operating from the shadows to secure the Eldians' freedom from Marley in his own way.
Rod later explains that Grisha entered the chapel seeking Frieda's Titan power, and they fought one another in their Titan forms. Rod says Frieda possessed an invincible power but did not have the experience to use it to its full potential. Therefore she lost to Grisha, who ate her and thus stole her power.
Zeke actually cares for Eren. He suffered from Grisha's bad parenting and thinks that Eren too was brainwashed by his dad. He sympathizes with him and thus wants to help him undo this.
She was caught committing treason against Marley, therefore turning her into the Abnormal Titan that would later eat her husband's second wife, Carla Yeager.
While Grisha did not entrust her with knowledge of the outside world and the two had their differences on raising their son, he did still seem to love her no less. This was shown in Eren's memories of Grisha injecting him with the Titan serum and in confusion tells him that Carla's death drove him insane.
His conflicted understanding, fueled by his grandfather's pacifist mindset and Grisha's radical teachings, led him to believe that only complete annihilation of the Eldians would bring them peace and salvation.
Grisha had good intentions, he genuinely wanted to save Eldia but the way he went about with things was questionable. He was a horrible father to Zeke. Grisha's own aspiration drove him to become the father he was.
Grisha sees future memories of The Rumbling, thinks it's terrible and tells Zeke to stop Eren. Grisha then proceeds to give Eren the Founding Titan anyways, despite telling Zeke to stop Eren. THEN, IN CHAPTER 137, GRISHA RETURNS TO FIGHT AGAINST THE RUMBLING!?! So if we follow the chain of events.
The feud between Marley and Eldians is long, full of horrific war crimes and an understandable resultant hatred of one another. Eldians once used the power of Titans to conquer the world by drowning it in blood -- a war in which Marley especially suffered.
Grisha believed in his son's ability so sincerely that he allowed himself to be devoured, believing that Eren would one day use the powers from the Founding Titan to control the Titans outside of the walls to fight back against Marley.
Grisha Yeager's basement (地下室 Chikashitsu?) is beneath the Yeager family's house in the Shiganshina District. Supposedly, it contains materials for Grisha's work as a doctor; it actually contains three books that reveal the secret of the Titans, Grisha's past, and the world outside the Walls.
