Maybe "manipulated" is not the right word. Chris was used to someone making the decisions for him, and doing things for him. His parents, and then, Shanann, who ran the family budget, and it seems, made the most decisions about the house, the kids, etc.
Actually, his affair and the need to do something about it was probably the first time the responsibility fell on Chris. And the only time Chris was trusted with own decision, he chose to annihilate his family.
Maybe there is a reason why no one, ever, delegated him with making own decision, why he was a pampered child? Why Shanann told him what to do and bossed him around, per coworkers? See what he did when left to own resources!
I hope they perform neurocognitive tests for CW.
(It seems they liked to Google in life-changing moments. Perhaps if CW merely Googled, "I don't love my wife. I am straddled with debts. I have an affair with another woman whom I think I love dearly and my wife does not know, but is starting to guess. I want to marry the other woman, but I have two kids, and third one on the way. On top of it, this woman is my coworker. What should I do?", and went with Google's advise?)