Here’s my massive, wild and crazy theory about the SNK world’s history, aka how it all started.
Four scientists or scientists’ families plan to create a place, or “perfect paradise” where a few families or bloodlines can live in while they leave the rest of the world to their doom by creating Titans, and few families will stay in peace inside the walls they have created. They want to do this because they believe that this is the solution to all the chaos and destruction of nature, as technological advancements may have affected the environment greatly. I believe that Titans may have been of help with keeping the environment clean and not harming any other organisms except humans.
Meanwhile, these are the scientists/their bloodlines:
1. Ackerman (Their group leader (?))
2. Reiss (First King)
3. unknown (Beast Titan)
4. unknown (created the Warriors’ village aka RBAY’s hometown)
They plan to manage a government inside the walls, create abilities/modify their DNA’s to gain abilities to manage this government, and pass these to their descendants to control the humans they’d rule over.
The Reiss scientist is given the ability to shift into a powerful, massive Titan, to wipe/modify memories, pass the first scientist’s memories and ideology to their descendants and also the responsibility of ruling over the people.
The Ackerman scientist is given the ability to be exceptionally strong, much stronger than average humans. They have the ability to be unaffected by memory wiping.
The third scientist is given the ability to turn into an intelligent, apelike Beast Titan that could communicate properly. This scientist is given the responsibility of controlling an army of intelligent Titan Shifters, them also being able to talk. He knows how to turn humans and Shifters into mindless Titans.
The fourth scientist, however, is given the responsibility of controlling a second, much bigger Shifter army, and also being unaffected by memory wipe like Ackerman.
This is where trouble starts.
There was an important ability needed to carry out the plan, and this was the Coordinate. The scientists were trying to figure out who gets this ability.
The Ackerman scientist announced that this would be given to #4 (maybe they are close?). The others went with it, but they were unhappy. Reiss and #3 thought that they deserved the Coordinate. They planned to work together to get the Coordinate from #4 and being powerful by eliminating the Ackermen and gaining their abilities too. The two worked together, knowing that only one of them would get it in the end.
The plan was carried out, only few families got into the walls, while the rest of humanity was left to die, terrorized by many mindless Titans of different kinds.
A memory wipe/modification was supposed to happen to avoid rebellion (I’m assuming this must’ve been only effective within a single place and that only Ackermen and #4’s people were immune to this, and Reiss spared #3 from memory wipe.). This was also the part where #3 and the Reiss’ plan was going to put into action.
The Reiss modified the memories of general society, making them forget the past, also convincing them that the Ackerman families were evil and had done a serious crime against humanity, making them think that the Ackerman families planned to turn traitor on humanity, as #3’s army suddenly launched into battle against #4’s yet-unprepared army, and gaining the Coordinate.
The Ackerman families were persecuted, while the remaining survivors of #4’s families ran off and made a small village outside the walls, also taking in humans from the outside world to form a plan someday to gain the Coordinate once again and free humanity from Titans, destroying Reiss and #3’s families forever, then saving the Ackermen, who were on their side.
The Reiss, knowing that they were probably being tracked down by #4 survivors, hid and let the Fritz family be the puppet government. #3, meanwhile, now had the Coordinate. The Reiss then hunted down #3, as they were the ones who knew the Walls very well. Eventually, they found one another, and the Reiss soon won, getting the Coordinate (maybe manipulating the military branches into fighting for them? idk, Code Reiss, eh?). There were other Reiss out there, though, and they made the Wall Cult.
But the #3 scientist aka Beast Titan, was somewhere else, knowing that his army might lose and so he abandoned them (though they didn’t know that), only bringing a few of them, and somehow turned them into mindless Titans, not knowing that they could still speak. They found #4’s group, aka the Warriors, and the Warriors forgave them.
Some of the mindless Titans made by the BT before were turned into humans, and they had children and grandchildren and such. The rest of the #3 army that survived against the Reiss found BT and remained loyal to him.
Ymir was a descendant of BT’s army. She was going to be crowned the new leader of the BT army when they found out that BT had abandoned them on purpose during the battle against the Reiss and wished for a new leader. A few Reiss spies that didn’t want anyone to know the Reiss secret hunted them down and killed them, while the others had their memories modified, and turned into mindless Titans, of which Ymir was part of. The Reiss might have manipulated BT into turning them into mindless Titans and ran off, also leaving BT not remembering much.
The rest is certainly what we know now, like Ymir getting to eat a titan shifter aka Marcel, and that the titan that ate Ilse was one of those former Ymir supporters whose memories got modified and was convinced that Ymir had been a traitor and turned these supporters into mindless titans.
The Warrior youths in this generation aka the Warriors that were going to carry out the plan about getting the Coordinate, didn’t know about the Beast Titan, first four scientists, etc. but their parents know, yet preferring to keep the story behind the mission secret, to prevent any complications so they won’t lose sight of their main goal, which is gaining the Coordinate, bringing it back to their hometown, then leaving the rest of the mission to the adult Warriors. (Who would then save the Ackermen, destroy the walls and freeing humanity from evil Titans)
So…I hope anyone who reads this liked my very long theory. I apologize for this being messy. It may have plot holes somewhere, but it’s what I could come up with at the moment.
P.S. I believe that Grisha was a Warrior that was part of the Warrior mission, and his task was to kill the Reiss and get the Coordinate for Eren, who’d be kidnapped by Warriors. I am still trying to fit Asians into this theory though…