>>513527096Drugs.
Drugs destroyed his brain. You see what happened to him a lot. People who do a lot of drugs in their late teens and early 20s, when they finally stop they lose their personality. That is because so much of the mental development that occurs for everybody at that age occured for them while under chemical influence. When you take those chemicals away the brain gets disoriented and in a way forgets a large portion of the mental development that it achieved despite the drugs.
But now you're too old and your brain too inelastic to repeat the process of mental development that is supposed to occur during late adolescence and early adulthood.
I think with Eminem this reality is heightened due to a deliberate choice to stop even trying to have a personality at least as far as his public persona is concerned. You can still see flashes of the old Em in some of his later records, but for the most part I think he just fully embraced the autistic wordsmith persona cause he knew he would never actually have an interesting story to tell ever again.
It's pretty sad shit.