I am not sure, there are so many things that lead to the unbalance of some parents minds when it comes to taking care of their children.
sometimes they are very young as your mother was Crafty so they think they cannot find the time or financial means of raising a child. Sometimes they have sex without protection and the baby was not meant to be.
They want power and control and like men who beat woman or sexually molest children it makes them feel powerful when in reality they are cowards because they cant pick on someone their own match and size.
I do not know, because I have never really seen it, only heard about it, is sad and heart breaking to read about this. Most of the time its the mother for some reason. The mother naturally seems to be more with the child and the mother becomes stressed and then there is baby blues (forget the word for it) , depression, but there is always help and courses. There is no excuse for any of this. Single mothering.
Look at the very first case Susan smith, years ago, she asked the world to pray for the return of her kids, she said they were carjacked, when she actually drowned her kids while in the car. How sad, Casey Anthony, the little girl Jonbenet Ramsey, I believe it was the mother also, she is passed away now.
I guess its like anything else in the world, we really do not understand why people do the things they do and probably never will, we can only hope that we can heal the world for the future of our children. Nothing is justifiable when it comes to this situation.