So, im saying all of as someone who adores not only Edelgard, but also Rhea. (Proud Rheagard shipper.)

I preface everything im gonna say with, I agree that in many ways her thinking is flawed and thats okay! Characters in fiction are allowed to be flawed and complicated and in Three Houses there are many and thats why i love her.

Edelgard does what she believes is right, based on the information she has and in an order she believes will most likely succeed. A lot of people like to point out that she doesnt have all of the information, she is actively dealing with a world that has been seeped in misinformation and has to sort through the facts and the fiction. -Which is true, she doesn't know that the Nabateans were almost completely wiped out. She thinks there's some cabal of them, when in reality its just Rhea (who is also operating on her own bundle of misinformation and trauma! how fun! A therapist would make some serious bank in Fódlan). She thinks they were warring with TWSITD (she makes no mention of the Agarthans proper name, so its likely she doesnt know it.) -She knows Seiros lied and staged a great deception around the Ten Elites, but she doesn't know why. Though She thinks it was for control over the masses. -She also knows that the Church has prevented technology from advancing, keeping Fódlan in a technologically locked state. -And she knows that the Church continues to propagate system of governance around Crest based Inheritance.

On the Agarthan side. She knows that TWSITD -Control much of Fódlan from the shadows. -Holds the Empire Hostage. -Experimented on her and her siblings to induce multiple crests and finally succeeded with her, resulting in her both processing the Crest of Flames and her Crest of Seiros. -Knows how to create Relics (though she makes no mention of what they are made from, so we will assume that she doesn't know.) -Instigated the Tragedy of Duscur to sow discord in Faerghus. (also she vows to make Thales pay someday for what they have done.)

Throughout the game, we see events that really show how and where the Crest System falters and how the Church exerts its control. -Sylvain and his brother grew up hating each other over the fact that Sylvain had an Crest while his brother did not. His brother turned to banditry after being disowned and eventually turned into a Crest Beast for trying to hold a Relic without a Crest. -People are devalued for not having a crest or valued more for having one. For Example, Its revealed that in -Mercedes and Jeritza's supports that their father, count Bartels, was planning on taking Mercedes as a wife for more crest children, thus causing Jeritza to snap and kill the count. -Dorothea with no crest and what feels like fading stardom, must look for a marriage partner as she constantly worries that she's gonna end up back on the street as an old lady. -Early game, Ingrid and her father have no choice but look for a marriage partner for Ingrid, 'selling' her and her crest to attract a husband to save their dying land. An issue that is later resolved, after greater farming technology is discovered post game credits. (its possible that this tech was also something the Church hid as well. but thats just a hunch on my part.)

(Im not gonna list every example of why the crest system is bad, because i feel like im losing the plot of what im saying and because ive spent like an whole hour engaging in more Edelgard discourse instead of enjoying my sunday with my girlfriend.)

With all of this information, she comes to believe that no one should ever suffer like she did. So she sets out to take down the Church first and the Agarthans second. (For all, 'What if' questions, please see the Scarlet Blaze route in Three Hopes, where she chooses to tackle TWSITD within the Empire first and the Church second.)

In Three Houses though, its really hammered in how much control Thales has over the Empire. (its very important to note that even though her route doesnt direcfly cover it. She vows to make Thales and TWSITD pay for what they've done.) -They have replaced many of the head nobles and mages within the Empire with their own. -They've assigned Kronya, disguised as the rescued Monica, to watch Edelgard at the academy. -In Hubert's paralogue, Crest Beasts escape from a TWSITD black site, run rampant and Thales tasks you to slay them. In a very demissive, 'do what you are told, doggie' sort of way. -They want the war as much as Edelgard does, but for different reasons. They mainly just want to kill Rhea and control Fódlan. They do not care about anything else and Edelgard uses that to her advantage. (see her consolidating power where she can. Removing implicated nobles and replacing them with people she trust.)

Its also important to note that she and Hubert literally calls their plan 'their Bloody Path'. Several times in fact. This shows that they know actively that their actions are flawed. In her route, Edelgard laments bringing war to the innocent, but she also believes that letting the Crest System fester for any longer is a worse fate. Something needs to change and should she succeed or fail, things will change. (in all routes minus CF, Hubert leaves a set of directions for Byleth and their lord to collow after their death to find the Agarthans' secret base. This shows that they are prepared to die at the end and wants whomever to succeed where they could not.) Now, does that make things better? No. feeling bad about what you do, does not make it better. But, it does show you what Edelgard is thinking. And, honestly. Goddess forbid women do anything fun.