As a counter-example, average IQ at the workplace is 110. Where’s everyone under IQ90? Injured, suicide, drug addicts etc.
[2] For your other claims about low IQ. It is "correlated" with lower lifespan (bit different than what you claimed but causes are similar) since you didn't cite.
You can find studies explaining high IQ with differences in environment or income and others point to genes. Some studies claim the choice of [3]toys your kids play with correlates to their IQ and success in life while others ask you to find a good genetic match.
Depending on which camps you are in, IQ could be highly related to the poor condition of the society.
* -15 points for not getting a healthy diet and regular health check ups in your childhood.
* -15 points for lack of proper education, social and family structure in your childhood.
* -17 points for mental health problems, unemployment, poverty and limited freedom after you become an adult.
Those issues overlap with each other regardless of IQ. Although, you can argue Intelligent parents can change these outcomes and if you believe IQ is heritable, then it makes perfect sense. You can use that to explain your bias.
Historically, evidence has been carefully crafted to promote products, services, aristocracy and many other things. I believe a lot happens now too with a different vector (China manipulating their averages) so I think IQ is not a good metric for looking down on people and explaining other circumstantial problems.
1] https://www.healthline.com/health/average-iq
2] https://www.scientificamerican.com/article/research-confirms...