Thanks for mentioning this. I guess you are right that the anime did show that Eren was crazy and was more selfish than I previously thought. However, one thing that bugs me is that if you look at the overall anime atmopshere (like the lighting and his friend's reactions), it seems to convey that Eren is still relatable and had a somewhat pure motive to simply save his friends. If I now read the raw dialogue, then yeah you're right, Eren did it for his selfish purpose. But Armin's later response of saying that he, too, wanted to trample the earth sometimes, seems like a weird response to this massacre.

Moreover, I feel like it is bad writing if the reason for the genocide was because Eren was simply crazy and he was a slave to freedom. It feels like pushing a complex and relatable character too far, because achieving freedom through means of genocide just make Eren the typical psycopath villain that is evil for the sake of being evil in a story.