Eren is and was never about any of that "peace" shit.
He just wants to survive, at any cost. And yeah he doesnt want his people to die (people of paradis, and specially his friends). But he developed a very "i did what i had to do" mentality in the process.
He also became extremely hopeless. Whether because he saw the future and how all would lead to this no matter what, or because he observed long enough to realize (and he actually points it out this chapter) that the world wouldn't forget generations of prejudice agaisnt the Eldians just like that. And even more so If we keep in mind the world wanted and excuse to wipe them out the planet and steal their resources.
The plan of sending Reiner and co to get back the coordinate? It was basically Marley trying to keep titan power to themselves while continuing to oppress the Eldians in the mainland. It was just a way to keep an asset for their country at the expense of Eldians. When this failed, it gave another reason to nuke/attack Paradis.
It was a "damned if you do, damned if you dont" situation. If Erwin had been alive, MAYBE they would have been able to use his charm and experience to talk to other people and form better diplomatic relations. But welp they didnt have that. They tried to rely on a Marley representative (??) Of Eldians but in the end they just shat all over Paradise (that one scene when Eren just leaves lmfao).
My point is Eren KNOWS he is being an extremist asshole, but what choice does he have? He didnt see any hope for his people to survive in the current political environment. And again, is not even about any actual peace, because they all know that the people in Paradise will have some beef with power at some point (I mean look at what happened when they kicked the royals out).
I think the entire picture is really complicated, but I apprecite the author really showed Eren's reasoning and how he knows what he is doing is fucked up, yet he will do it because he is that much of a hopeless, angry bastard.
@RC1138Boss He doesnt give a shit about peace. He just doesnt want to die first or give them the chance so he will just nuke the whole world because he is angry and has no hope anymore.
@OnePunchDio It gets explained at one point that titans are actually lighter than they should be and thats why they can float. The funny thing is that they swim, I guess because Eren is controlling them.
@Watapon This is actually a super interesting thing. Marley is oppressing and has been oppressing Eldians for generations, but they continued to further delude themselves in this victim mentality. You cant change something so systemic like what Marley had built in so little time.
Also smart move on Eren's part to keep his seemly frail titan body sorrounded by the titans so the absurd amount of heat acts as a "fuck you" barrier. I wonder If they will try to drop bombs on him from a plane though.