moscone would've sued jack

When Jack let the Duke go at the end, the movie wanted us to feel like Moscone got his comeuppance, and that he would be ruined and go out of business. It seemed to forget that Jack insisted early on that Moscone give him a contract. Since he got everything else, we have to assume he got that too. That contract would legally bind Jack to delivering the Duke per the terms. Moscone could prove that Jack could've fulfilled the contract but chose not to, thus violating the terms. He would've sued him for restitution, plus damages, since it was a willful act when Jack let the Duke go.