First of all, the Senate Healthcare Bill is not 2500+ pages. It's 2074.http://documents.nytimes.com/senate-health-care-bill
These are not pages packed full of content in paragraph form that read like a novel either. Even when they get into the meat of the proposals everything seems to be triple-spaced with gigantic font, they only manage to get 20 lines in on a page and those don't even consist of full sentences. If the formatting used was similar to a book, I can't imagine this even topping 1000 pages.
The first however many pages are the table of contents, there's tons of procedural language that actually doesn't say anything, and entire sections devoted to ironing out loopholes. This is the way legislation has to be made so that various portions are clearly accessible, the document conforms to legal standards, and everything is written in a concise enough way that it doesn't turn into a legalistic nightmare.
If the bill was too short, it would become a gigantic burden on the court system or the Health Insurance Providers would search for loopholes. Face it, you have to be verbose if you want to be concise. Look also at the fact that they tried to do an enormous amount of things within the bill (as listed by the table of contents). The length of the bill should not be a stumbling point; it's become one because the Republicans effectively made the argument that the American people don't know what's in it. Obviously it's size makes that argument easier to make, but poor communication on the subject really sealed the deal.
However, I don't think this was the way to go about things necessarily either. Issue by issue things should've been passed in smaller packages. Make the Republicans vote no to pre-existing conditions separately from other issues if you really want to show the American people that they're being obstructionist and/or pass legislation that actually helps people. I have to wonder why they went with the monolithic approach to begin with.
I've come to the sad conclusion that it was simply Democratic Senators looking to score a big win by pushing through a glut of changes that would give this congress a legacy to campaign on and look back at historically. They wanted to make this their civil rights legislation and now they have next to nothing to work with a the 2010 elections will most likely be a third party/Republican landslide. And yet I am not at all surprised. The Democrats are by far the best part at getting in their own way.