I don’t think that was the problem. Remember, he KILLED them. That’s not a rational act, even if you claim some heavenly justification. If you kill your family, there should be a good reason ie they stole your dope, you needed the insurance money or the always beloved “they just needed killin”. Killing your family for kicks sounds like a start to a life of serial badness.
Whatever happened to the old favorite “I don’t like Mondays”.
He was just bat’s ass crazy, the mystery is how he managed to compartmentalize it so well. If not for that one little incident...