I asked a man in prison once how he happened to be there and he said he had stolen a pair of shoes. I told him if he had stolen a railroad he would be a United States Senator.
In jail a man has no personality. He is a minor disposal problem and a few entries on reports. Nobody cares who loves or hates him, what he looks like, what he did with his life. Nobody reacts to him unless he gives trouble. Nobody abuses him. All that is asked of him is that he go quietly to the right cell and remain quiet when he gets there. There is nothing to fight against, nothing to be mad at. The jailers are quiet men without animosity or sadism.
I was in prison, and you came unto me. Verily I say unto you, inasmuch as ye have done it unto one of the least of these my brethren, ye have done it unto me.
~(Jesus Christ) Matthew 25:36, 40
Why would anyone expect him to come out smarter? He went to prison for three years, not Princeton.
I can tell you this on a stack of Bibles: prisons are archaic, brutal, unregenerative, overcrowded hell holes where the inmates are treated like animals with absolutely not one humane thought given to what they are going to do once they are released. You're an animal in a cage and you're treated like one.