Look, I realize they don't want to admit to themselves that grandpa killed his granddaughter, but it's his fault. It's sad and heartrending, but it's the truth. Grandpa messed up and a little girl is dead as a result.
Agree. As I said when it first happened, I think the finger pointing is practically an involuntary response by the brain to protect itself. This was a terrible tragedy due to some basic negligence. AFAIK, the grandfather truly didn't know the window was open. Had he known and still did this, I would have a different view. This was simply a "worst case" of someone not thinking, and he and his family are subconsciously looking for ways to divert blame.
He has to live with this the rest of his life, and personally, I think that's enough punishment in this case.