Eren suffered so much. They can't understand cuz they're not the ones who gets to see the memories of the dead crying for freedom and peace till their last breath. It drove him mad. It broke him. The kid who was once afraid of dying, saw countless of people died for one goal, is now unafraid anymore and is ready to face death himself for the very same goal. Maybe the thought of sacrificing his own life for the sake of the ones who sacrificed their lives to attain peace and freedom for the future of mankind is his only salvation. The outcome of the battle might be his peace and dying for the sake of it might be his freedom.
I'm so sad and mad for Eren... he really doesnt deserve this the marleyans had it coming for them. They just barged in and destroyed the walls resulting in so many people dying for absolutely no reason. Ppl who didnt even know that other humans existed and now we're supposed to watch marelyans win and survive this? Im honestly so mad they cant go around killing the island ppl, declaring war one sidedly and deciding to annihilate them but the moment they fight back then they're evil and Eren should be killed? This is honestly bs i cant stand how this is going to end It's so unfair for eren....