Just look at Fetterman. Had a stroke, and he’s now conservative.

That's true, it's a combination of factors. A big part is the insular nature of the team and coaching as you go higher up the ladder. If you're not thanking God in your post-win interview you're a "locker room problem"; if you want a coaching job after you retire you've gotta be on good terms with the good ol' boys network.

I do think that the brain damage does compound heavily though. I know Mormons who get out and become well adjusted people later in life; the semi-pro football players I know get more irrational and violent as the CTE sets in.