Well, here are my 2 cents. They may or may not have value.
If I have my timeline straight Chris was probably around the age of 10 when his parents became Christians. Grace Bible Church's first meeting place that wasn't someone's living room used to be a bar, a bar that was not completely unfamiliar to his parents. I remember RC talking about the irony of 'I used to sit on a bar stool over there, and now I'm behind a pulpit up here' or something to that effect.
There is nothing 'wrong' with going to bars. There is nothing 'wrong' with not being Christian, and neither of these acts are going to turn your son into the kind of person who murders his own family.
But, and this is something that was honestly in my head ~15 years ago, maybe Chris already had his outlook on life set by watching his parents live what was by all accounts a very 'worldly' lifestyle. Maybe he was already destined to be more comfortable living that lifestyle than the strict 'oldest son of a respected preacher' that he was thrown into.
Maybe after living what might have felt like a lie for the last 20+ years he couldn't do that any more. A divorce would embarrass his parents, and probably cost him the $100k/yr job that he was very unlikely to ever replace. And he snapped...
That is the only way I can explain, to myself, the CC I knew having done this.
Here are my thoughts...
CC is getting tired of having to live under so many rules - he simply getting sick of his religious life, his religious wife & children, religious family, religious employer, religious social circle.
He wants out of all of it and he wants to go play the field and find out what he has been missing out...
straight out of HS, becomes a Marine, meets a beautiful USAF gal, she gets pregnant before they are both out of the service, probably gets married because or family and military pressure, gets out of military moves back around family, daddy C lines him up with a good job with JM, wife starts enjoying the religious life. Wife starts getting more appreciate by others than what he is getting (or thinks he deserves it more), she has a closer relationship with boys than he does. He starts disliking his children, he starts disliking Sheri, he starts disliking his employer, his family, etc.
He does not want to pay alimony nor child support. He wants a free break.
He comes up with a plan... I'll write threatening letter to make it look like someone is threatening my family because I work for JMM.
I'll kill my family and I write things on the wall to make it look like it was hit all because I work for that "B", JM. (I recall someone said she-devil was on the wall in the house)
I'll get away with it and I will collect the life insurance and then I will sue JMM because they did not protect my family from these threats or the killer(s).
I'll sell my house and disappear with my bank account and pockets full of cash.
No wife and no kids to deal with - no employer to deal with - no family to deal with.
I will be able to retire and I will get away with it.
Typical narcissist...