Everything starts with Jerry needing money, but as he shows throughout the movie that he does not plan or think many things fully through. Therefore, his plan to get a lot of money fast, is to get his wife kidnapped, and have demands for her rich father to pay for her return.
Jerry is shown as a nervous, none emotionally attuned man who put himself before everyone else whether intentional or not. His lack of connection is shown through more than just him freaking out over things not going his way. When his son is terrified about his moms disappearance, he gives his son no sympathy.