When I was depressed I didn't talk about with people, even family members, until things blew up in my face and I had to talk about it. My interior dialogue usually included these kinds of lines. "Why talk about it with others? They've got far more serious things to think about.I'm not important." "Its not really depression I'm just feeling down a little. I'm okay really." Hell If I want to kill myself its because I'm not worth anything alive." Better if I don't say anything because it just upsets people and then they get hysterical or think I'm just saying it to get attention."
Part of being mentally ill is that you don't make the best decisions that could be made. You don't always make the wrong ones but you're not thinking the same way you usually do. Wondering why the mother didn't do any number of sensible things doesn't help because she wasn't able to make consistently sensible decisions. Ideally the father should have been able to make many of these decsions himself but he probably didn't know what he needed to do. The father may well have thought that he was being supportive but was instead woefully ignorant of what kind of support was really needed. He may also have made lousy decisions because of stress and embarassment.