How or why Scott Adams went completely of the rails is perhaps something we'll sadly never understand. Was this opinions he'd always had, but suppressed, did he somehow become radicalized or was it perhaps medically induced, e.g. a stroke or something. It was incredibly sad to see him throw away his life's work and go down a path most of us at least hadn't foreseen and die having alienated his fans.
It’s so common that we barely remark on it any longer. So I don’t think it’s really a mystery, it can happen to anyone who’s not getting outside enough.
My first clue something was wrong was when he didn’t understand the criticism around the Iraq war of the early 2000s. Which even most conservatives have come around now to acknowledge as a disaster.