Wow. I love how you took that one bit (that deviates from Rational Choice) and came up with very good reasons why he did what he did.
If he in fact had a habit of hot prowling, that would fit Rational Choice Theory (get the facts, make rational choices). For those not familiar, this is a theory about how to reason out a better crime, weighing the risks and deciding the odds are on one's own side.
Originally, I thought the theory of "just went into a frenzy" when things didn't go his way was a bit out there, but the more I read about RCT (not used by criminals - used by criminologists, interestingly), I am beginning to see it your way. If he had done multiple stalking forays, this makes sense.
One can almost sense the rising tension, in your account. He sets out from Pullman at 2 am'ish, as he has done before. He is getting more and more excited (and has started to shut his phone down as he approaches his hot prowl target). Much like Joe DeAngelo (and FWIW, also Joe DeAngelo's brother, according to some sources). So he turns his phone off, not quite sure of what he intends to do (possible). But he has made contact with MM via Instagram at least 3 times before this (I posted the link earlier).
He's energized, amped, scared, etc. He finally parks. He does NOT expect to find the house awake and so "crowded." He HAS thought about what he will say to someone in the house if he encounters them, "Don't worry, I'm just a friend" or similar.
Wow. Makes lots of sense. But it becomes a motive that's elusive for LE and the State, for sure. I will now posit that there's a psychosexual thing going on in this crime (regardless of who did it). It's not overtly sexual, but it is definitely a man who committed this crime, IMO, and three women who died (Ethan is collateral damage). I also believe that if this ever comes to trial (and I think it will), the jury will be asked to weigh in on facts (from the autopsy; hinted at by SG) that may be pertinent.
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All speculation of course. I tend to use actual models of other past, proved criminal behavior in my analysis. I think your analysis fits with all that.
I was very unconvinced by the "he might not have intended to kill everyone" scenarios early on, but I've come around. I am still on the fence, but I do think he might have had MM as a kind of "target." For me, if his acquisition of the Ka-Bar knife was recent (after he moved to Pullman), that's big clue as to his state of mind and his criminality.
IMO.