What made Orochimaru turn kinda good-ish during the war?

I just got done watching the ep where he heals Tsunade, and don't really know what just happened.. his reasoning for why he was doing it was riddled in metaphors I don't understand. What made him have a change of heart and want to help the Allied forced, Not want to take Sasukes's body (instead see what way his "wind will blow"), and not destroy the Leaf village