I agree that none of these were "bad mothers," but I have some anecdotal experience, having seen the effects "first hand."
A friend of mine's mother got married very young and had two children. She soon divorced. When the kids were teenagers she remarried and bore three children with the new father.
Of the three new children of the new father, all graduated from college. One of the three went to an ivy league University and ultimately became a millionaire, while another of the three works on wall Street.
Of the two earlier boys with the different father, both have spent time in prison and one of them is homeless. The other has worked odd jobs for years, barely keeping his head above water.
I will admit that I do know of a single mom who has successfully raised a child, but her situation is not the norm. She is wealthy, works from home, and her child is a girl (boys tend to be the problem).
But I still feel her daughter could have done more. The fathers of the kids I know have turned their kids into chess champions and Harvard bound competitive tennis players. I know the wives and while they are very attentive to the children (they work from home full or part time), it's been the coordination of the fathers that have pushed the kids to much greater heights. These kids could never have achieved what they have without him.
I'll add though that the husband's relationships with their wives are far from perfect, perhaps even slightly stressed. But they have worked together to raise extraordinary children. My wish is that if you insist on having a child, choose a man and accept that you may not be attracted to the man at all, neither looks nor personality, but instead focus on the values he places on family. If you must have a child, then you should be the one to suffer the sacrifice, not the child.