I work for a mental health organization and this morning we got a crash course in postpartum depression. Clinical depression can have a psychotic component to it, which causes people to do very strange things. It is extremely rare, but it does happen. Apparently Mrs. Yates had already experienced psychotic episodes because she had been taking Haldol, which is an anti=psychotic drug. The doctor took her off it just a few days prior, as I understand.
Anyway, a person in a psychotic state is experiencing what you might call an alternate reality. In her mind, she had to drown those children, for whatever reason. Yes, it could take awhile to kill 5 kids. We are rational thinking people and to us it simply doesn't make sense- but to her, in her psychotic state, it made perfect sense.
Saying the father may be involved because his outward state of grief is seemingly unacceptable, is not right. Everyone has different ways of dealing with bereavement. Some people weep and wail and others wait until they are behind closed doors. Even in our modern society there are still men who don't want to cry in public.
This man was trying to provide for a large family. He was getting treatment for his wife. It didn't work. It is simply an awful tragedy all the way around. I don't know what the answers are.