I think a lot of the problem is environmental/societal.
If you have never heard of it before, check out the Mouse Utopia Experiment. In this experiment, many generations of mice were raised in a habitat that should have been perfect for mice. In the first several generations, the mice thrived and the population grew. But at some point, long before the mice ran out of food or room, the population leveled off and the mice started exhibiting aberrant behavior. Their reproduction rate slowed down, males became obsessed with their appearance, females lost interest in raising their pups. Eventually, the mice barely reproduced and the colony died.
This experiment was repeated several times, with mice and rats, and the outcome was always the same.
I see a lot of parallels between the mouse behavior and human behavior. In my opinion, the mouse habitat can be likened to a city, and liberal behaviors are an outcome of being raised and living in environments where there are too many people for optimal social development.
It’s entirely possible both theories are correct.