You can have your mirrors adjusted properly while still looking over your shoulder. I posted above that I was taught how to properly adjust my mirrors I I’ve never had blind spots, but I still always look over my shoulders - including opening my door as the Dutch do (open the driver door with your right hand, not the left, because this forces you to reach across yourself and thus turn to see what might be coming towards you and you might open your door into)
My theory is that him and Adam Baldwin were both on the outskirts of these conspiracies, then when they were in a show together (Chuck) they started talking together and it spiraled and they both became crazier and their combined crazy fueled each other. If you look at the trajectory of both of their craziness, it seems to line up with the second half of the series and afterwards.