Hello everyone,
I got a lot of information about why he did it from the Live Abuse Free YT channel, there is a whole playlist on there, and my own research into narcissism. Chris is a huge narcissist and he killed her to preserve his "perfect image". It is always better to be perceived as a poor widower rather than someone who wanted to leave his pregnant wife and 2 small kids for a mistress. He didn't want the kids because they started to develop their own personalities and did not consider him to be the "God" he felt he was. He didn't bother to develop a relationship with them and was surprised why they preferred their mother's company. He was jealous!
I really don't like how they portrayed Shannan in the Netflix documentary. What I find interesting is that Shannan was in an abusive relationship before Chris, so she was probably more vocal about what she did and didn't like. I think Chris was passive and didn't talk to her about important stuff, that is why she might have seemed to look controlling, but honestly I would be as well. She went away for a few weeks and he stopped communicating, just like that. She would have been just fine if he had told her he wanted a divorce. It would have not been easy financially and stuff but she would have figured it out!!! It was the fact that he didn't bother explaining anything and he kept telling her he loved her and ignoring her, but she KNEW something was wrong, and kept and kept on asking. She wanted to accommodate his needs till the end, like she was writing to someone that she wants to change for Chris because he could have been hurt by some of her behavior. What really frustrates me is how for example on IMDB, the reviewers keep saying how he couldn't handle her being controlling, etc., AS IF HE COULD NOT HAVE TOLD HER THAT in a normal adult conversation. But he wasn't able to handle one! Wasn't able to take the least tiny little bit of criticism and went straight into the narcissistic rage.