I don't think IQ has anything to do with the simple problem that people train for and gain experience in specialized professions (a cost of years, maybe a lifet

I don't think IQ has anything to do with the simple problem that people train for and gain experience in specialized professions (a cost of years, maybe a lifetime), but can find themselves poorly paid or out of work when the supply and demand situation turns sour for them. You don't have to be stupid to find yourself unneeded and unable to realistically respond to market signals.