You're not wrong in thinking his parenting is up to him no matter what.
But you're mind reading in thinking he couldn't be a better dad because he was with you.
He chose to leave because it was time to make changes. Whether or not he needed to make those changes entirely because of your behavior or only partially, they most likely were a catalyst for other changes that he needed to make. So he's making them.
Whatever his reasons, the healthiest thing you can do is appreciate that he IS present for your daughter because this will make it all easier for her, however things turn out.
Me42, H40 D12, S8, S7 A revealed: 7/13 Sep 4/14; Agreed to D 1/15