1. You did not explain the main question clearly.
2. You did not tie your work to what had already been done.
3. You did not explain how your experiments would address the question.
4. There was a flaw in your reasoning, or it was insufficiently explained.
5. Your proposal was so unclear, disorganized, or sloppy that it was hard to tell what you wanted to do or why.
6. Your big question was not very exciting or conceptual.
7. Your conceptual introduction did not match the experiments you propose.
8. You proposed a method to do something that it would not do.
9. The proposed research was not a sufficient advance on your previous work or that of your advisor, or you did not indicate the relationship.
10. Your Broader Impacts section did not go beyond what you saw as the intrinsic worth of your work.
The strongest proposals did not have any of these problems. The weakest proposals had several of these problems. You may be discouraged now, but fixing these problems in the DDIG and in your work generally will help you overall. The best studies address important problems, show a deep understanding of the literature, do clear, effective experiments, and write up carefully. The more you read and write, the better you’ll do. Plenty of now-famous professors did not get their DDIGs funded, but learned from the thoughtful comments on them and applied what they learned to their research.