Board Thread:Manga/@comment-33485746-20171102190256/@comment-33485746-20171103005706

18 years would actually explained a lot.

in 845, Grisha's time is almost over, that's why he wanted to show Eren what's in the basement and maybe he was going to give the Attack Titan to Eren. But he didn't expect the Marleyan to attack them at that moment.

Carla's death flipped his switch, and instead of JUST giving Eren the Attack Titan, he went staright to the Reiss family and stole the Founding Titan himself and gave both of the titan power to Eren.

Nevermind, Isayama-sensei is without a doubt a genius.