It's not mutually exclusive and, to avoid a double ping:

He definitely was successful in brainwashing people. I don't want to minimize dangerous people like him

This overwhelmingly is not what his job actually was. His job was pretending to get youth support so his mostly older audience felt better about themselves. He was a slopagandist whose job was to preach to the choir, which is harmful but for a different reason

Incidentally, brainwashing isn't real and one person doesn't have the power to enculturate you unless you are locked in their basement or something.