Is he having an affair? Does he want something from you?

Great to hear he seems to take it seriously. But I do wonder what made him change his perspective: in my experience, not believing in mental illness (I don't even) is deep-rooted, having much to do with a firm, "therapeutic"/"anxiolytic-rational" believe in control (for me the reason is different: I firmly believe in never having any control).

Edit:
It could just be his "self-transcending" intelligence or wisdom, though. He probably shares that trait with you.