Socio-economic status is one of the prime predictors of IQ.
The behaviors associated with lower IQ are those that tend to promote and sustain poverty.
Particularly with a statist support system that removes the necessity of one being at all responsible for one’s basic survival.
Combination of things. Statist support system for sure. Plus government schools that indoctrinate instead of educating children. The lack of moral core values that were once instilled , if not by parents, by the Christian community. The work ethic and the liberating self-respect which comes from Christianity was the backbone of America until the 60s.
I think you have that backwards. IQ is a predictor of socio-economic status. Being intelligent is no guaranty of prosperity, but being mentally challenged is a certain path to living at the bottom of the economic scale.