I keep thinking that one of the gremlins was when he was switched to a different ATC ... the first one had guided him to skirt Van Nuys .... circle for 12 minutes or so .... then up to the highway and turn left toward destination.
Right around the time he was approaching the foggy valley crossing he had been switched to a different tower and had to tell them where he was and where he was heading .... right when he was intensely focused on what was in front of him .
Call it a minor distraction or whatever .... but our brains lose focus when we communicate by phone or radio while driving or flying.