No body means you cannot confirm he's gone. Either he killed mother and died along with her, or he survived with her. Grandfather needs a suitable host, and he needs to be alive to get one.

( he's hoping that, regardless of whose world it is, that talia managed to survive regardless of ra's presence in her body. that she managed to wrangle control out from under him in time to survive, because damian's mother would not be erased so easily. because she deserves better. )

She loved you, and you couldn't even manage to save her.