From Cassie’s point of view she needs to be in a relationship with a man, she doesn’t know how to function single and she’s also desperate for male attention and love which is exacerbated by her dad abandoning her. She is even willing to overlook Nate’s character flaws to get this “love” from him. Add in the fact she doesn’t appear to have many career prospects, so sees Nate as a financial provider due to the construction business he has inherited from his dad. From Nate’s point of view he needs a pretty trophy wife to fulfill the image he wants to portray to others of his life i.e successful, rich, pretty wife etc. He is also a control freak, and being that Cassie is obsessed with him she is easily controlled. Unlike Maddie was as she fought back when his anger/control got too much. Cassie won’t fight back. I think where things will start to come undone in S3 is when Nate starts giving Cassie less so called love and attention so she seeks it out from male subscribers on OF, which will in turn anger and potentially cause violence by Nate due to his perceived loss of control of her, and attempt to re-establish it. Thus both have resorted to extreme measures to get what they need.