so what was the psychologist arguing for?
He wasn't arguing for anything. He was simply illustrating by a real life example that, regardless of a person's background, they do have choices in life. Using your background as a crutch to become a criminal, be a failure, etc. is a self-limiting choice, not a foregone conclusion.
So the psycholoigst could ask what structures were implicated in one brother ending up in prison and the other being so rich as to be a millionaire?
If, by "structures" you mean what was each brother's thinking pattern, that is precisely the point of the story. One brother framed his background to mean he had no choice but to become a criminal just like his father; the other brother framed his experience to motivate him to be the exact opposite of his father.
In case you missed the point, each brother lives in the same country (USA) and grew up in the exact same circumstances. So the argument that a person's experiences and "geography" (growing up in a "thug-rich" environment) determine his life is pure nonsense.
I don't know if you are asking a clarifying point or looking for something to argue about. I related a true story. Either accept it or don't.
and what does psychology have to offer?
Really?