This video explains it well.
Basically, smart people tend to overthink, while stupid people act and get things done. This is why a smart person will overthink on how to approach a girl, while a stupid person will just do it. Smart person will also overthink about the world and science, which prevents him from putting more effort into getting girls. While smart person studies and does math, stupid person makes friends and gets girls. The current education system punishes smart people in every way possible. Smart people have to spend their entire childhood studying and working, thus their social skills degrade. This is why countries with highest IQ and lots of studying, like Japan, have such low birth rates because studying made people retarded. They forgot that the only purpose of life is to survive and reproduce. In this sense, the more education person gets, the less capable person becomes in having a family. This is because education teaches you specifically how to be obedient to the system and work, and thus pushes out thoughts about family. Whats even dumber is that stupid person is actually more useful to society than smart person, because stupid person reproduces much more and many of those kids will be smart, and those which are stupid will reproduce more and generally, with greater quantity of people, greater is the number of smart people among them.