I have some predictions of why King Fritz decided to do what he did.
Obviously all those of the king's bloodline who inherited his titan power were traumatized by the memory of the previous generations.
My guess is that the first titan, Ymir, started out with good will, to help her people. Later on, the people of Ymir might have gotten more greedy, and started experimenting on ways to make more titans. Then, there might have been a time when they did do terrible things using the titan power as the Marleys say. The king probably felt that the development of the technology of making people titans started the tragedy.
He probably felt that the titan power should be sealed so that it could not be used for greed or bad purposes, and at the same time protect his people with the walls. He probably felt (though he probably was half insane) that if the people did not know of the titan power and did not develop technology, they can live a simple life before there ever was a titan. He probably didn't want to use the titan power anymore.
And he did succeed in some ways, because for a hundred years they got to live without having to do with titan powers. Though of course it was sort of like procrastinating, like he was running away from what they eventually have to face.
About Annie, I don't think Reiner has ever forgotten her. But I suppose the higher ups decided they couldn't go for her.
Yes ... you're probably right. But his method of sealing giant powers has already become obsolete for some time ... since the first invasion, at least. And Christa's father witnessed this. And yet the descendants of the royal family, immune to brainwashing, continued with the theater of complete ignorance while many people died unnecessarily.
And unlike Eren's father, they even didn't leave behind manuscripts for the survival of the species. At least paint a crazy story like the Marleys did and faced the problem efficiently.
I don't know if I skipped a chapter, but is Annie still sealed in the glass? Has not the Hanji's team yet figured out a way to get the girl out and get more information about her homeland?
Seeing the current situation of Reiner I began to feel very sorry for these children.
Maybe Reiner will turn to Eren's side.
I think that Falco will betray Marley not Reiner
he clearly wasn't brainwashed enough
Is it my impression, or did they forget Annie in the prison dungeon?
And frankly I still do not understand, why King Fritz had to make the eldian people of the wall forget about their true origin.
It would be much easier for them to deal with the invaders having this knowledge, than to let them die in ignorance and still in a very barbaric way.