The narrative about men being desperate to pass on their genes and only wanting to provide for their own progeny so as to ensure the success of their children kind of falls apart when you look at the way so many men behave toward their kids.

I also read somewhere that many men think of their wife and children as kind of a package deal, and once a relationship falls apart, they have little further interest in the children from that relationship. Some of what you've said here seems to bear that out.