There is a false assumption that someone suffering this, or again any mental health issue, will show it on their face like a rash (that spells “nutbar” across their forehead, maybe?) or in their general, casually observed behaviour.
Bad things happen to good people. Bad people get away with shit they shouldn’t. Life isn’t fair, and we want to tear our hair out at it sometimes (and sometimes we do), but as a society, a generally even-minded culture of good people, we try our best to mitigate this and our failures are often pretty spectacular.