Totally agree! People who commit serious crimes generally have a history, starting with small crimes which graduate into bigger, more serious crimes. However, that is where family annihilators are interesting as some of them (eg CW, SP etc) don't have criminal histories. Their crimes appear 'out of the blue' but what you find is they have been fantasizing about it for quite some time. Not necessarily planning the crime, but in their mind they have thought about killing their families. An awful analogy is suicide, whereby people who go through with this have had a prior history of at least suicidal thought, which starts with fleeting thoughts and increases with intensity towards making a plan.
I believe this has been going on for awhile with CW. For instance, the picture of CW and SW, where CW is staring at her intently, makes me wonder what his thoughts were at the time. His facial expression does not look like love to me. Its intense and scary. Same with some of the pictures of those shoulder massages he gave her. It would not surprise me if he had been having fleeting thoughts about strangling her for quite some time. Likewise, his picture of the sheet over the doll was probably the result of his subconscious thoughts acting out in real life.
In the weeks leading up to his horrific actions he was barely sleeping. Anyone who has had babies knows what it is like to be so sleep deprived. It messes with your ability to have rational thought, your emotions and your planning skills. I do believe his lack of sleep would have influenced how well he planned and carried out his crimes..and may partially account for his absolute stupidity.