The opposite actually. His first year-and-a-half, maybe two years as a senator, his voting record was fine. He wasn't super radical, but if you look up voting record scores he was one of the more left-leaning senators until the end of his 2nd year.

The stroke happened before he took office. Aa fun as it is to joke about conservatism being caused by brain damage, it just doesn't line uo with the facts for Fetterman.