Pretty much every successful proposal starts with a variant of the following structure:
1. Topic X is important and interesting. 2. But. 3. This is how we will address "But."
The rest of the proposal reiterates those three points with enough detail to make it believable. In a short proposal, the structure fills a paragraph. In a long proposal, it's three paragraphs, and shouldn't go past the first page. The abstract is a 1 paragraph version of the same structure, with the addition of a closing rah rah rah sentence. If you can't bludgeon your introduction into this form, you might want to step back and regroup.