I believe that Noah was subjected to systematic abuse/torture, by his sperm donor. I believe the mother was at least aware and did not stop him.
I think Noah slowly died and that the parents fought over what to do as the child was dying. Dad may have kicked out mom and did not allow her back in because he disagreed with calling for help, so she may have been unaware as to when exactly he succumbed.
The mother would have had excellent grounds for custody against the father due to his apparent lack of involvement.
However, the grandparents would've had much better grounds than either parent, IMO, if indeed they had raised the kids most of their lives and if there were on-going issues with the parents.
The fact that the mother supposedly camped out and did not go for help earlier nor ask her parents for assistance indicates to me a level of not fear, but culpability. Maybe either drugs were at play or she didn't want to give her parents reason to try to get the kids back, IDK. But both parents were charged with the same crime, although there are two ways to get there - one is inflicting the abuse and the other is allowing it to happen.
I will never accept the abused spouse excuse for allowing a child to be harmed. No amount of fear of a spouse/partner could come close to the level of fear at my child being abused/killed.
I would kill any person who is harming my child before allowing them to continue to harm my kid.