It’s a simple truth: The easiest way to get a decision maker to approve a decision is to offer something that they actually want. Of course, the obvious question is: What do you do when you need their approval for something that they don’t want?
Try empathy!
Why are they right to not want it? What do they want instead? How does what you want align to what they want? How could you modify the idea you want them to approve so that it also gets them what they want? How does your idea contribute to them getting what they really want?
It’s even better to ask these questions before you actually build your project, your product, your proposal. When you do, all you need to do with your pitch is to tell a true story about the thing you’ve built.