After watching that youTube vid and the way he talked about sleep I’m thinking it is possible he had a sleep “disorder” and maybe, just maybe lack of sleep turned him psychotic. I have read a bit about this subject after having anxiety related to dealing with insomnia myself for years. If this guy had no sleep for days on end and was already mentally unstable, that could cause his rambling incoherent speech patterns and maybe even the eventual killing spree.
Sleep disorders don’t necessarily evolve into a human skull in the backyard. He was into drugs - courtesy of a cartel who also engage in mindless, heinous acts. He was a scary, left winger on a mission to kill people. His victims were all “typical” white people (what Obama calls them.) He didn’t shoot anybody else.