If fathers make such superior single parents then where are they?

I think you're wrong about the courts showing preference to mothers as well as your conclusions about mental health. That's based on opinion and sketchy statistics, not objective truth.

It seems to me the disparity is based on one thing. The single fathers who make the statistics wanted to be single fathers. That's what makes good outcomes for kids. Parents who wanted them and put them first, no matter what. And an extended support network of family and friends and community.

That's it.

If you look at single moms who meet those criteria, you won't see a difference. In fact, most reports show best outcomes come from single mothers who chose single Parenthood, prepared for it, especially financially, and had that network. But I don't think it would significant over the single fathers you chronicled.

The courts choose custodial parent based on primarily two things. Who the primary caregiver was before the split to provide stability during a time of upheaval and disruption. Men hurt themselves in court by not being more involved with their children from day 1 and leaving moms to handle so much of the daily care giving. The second thing is who they feel will more likely stick around and not abandon the child. This is because they don't want to burden the state with the care of an abandoned child by choosing fathers.

You may not like that idea, but the ease with which so many fathers drift out of their kids' lives when given joint custody gives credence to the notion. There is no "it's too hard" when it comes to your kids. You either show up or you don't.