The causes of low IQ are, in order:
Genetics
Genetics
Genetics
also brain damage and drug abuse.
IQ is pretty well fixed and is measurable by the age of three. It doesn't change significantly over the lifetime, except for a very gradual decline, mostly as the result of aging, drug abuse and minor brain damage accumulation.
Parts of West Africa have an average 65 IQ. That qualifies as mentally retarded in the US. That's the average. It is inborn, congenital, and cannot be increased.
Training a stupid person does not make them smart. It may make them better able to handle many tasks, but it will not make them smarter. Training them in the proper attitude towards Whites will not make them smart. They were born dumb.
These are simple, demonstrable facts, supported by over 100 years of research into the nature of human intelligence. You would rather believe the fairy tale you were taught than the cold hard facts of life. Fairy tales make for incredibly bad policy