I'm guessing it was partially about the completely bonkers story falling apart, or possibly something to do with the way it was coded. I forget exactly what the dev said was the specific reasons when they started the remake. But they did end up deciding to make new renders/animations from the ground up, rather than try to reuse as much of the old renders/animations as they could, and only make new renders for the new story beats so the updates wouldn't be so small and infrequent, but that was their choice I guess.
I still enjoy the game, and generally find the story in the remake to be far more coherent, but I definitely did enjoy the content in the original, and wish we could have some of that previous content in the remake already, given how long it's been ongoing. But whatever, it's still got some of the best looking renders (for girls of these body types of course) out there, in my opinion, so I'm alright with waiting, even if I wish the wait wasn't so long.