Why is it difficult for people to believe Rather was part of the fraud? Someone faked these documents, why not Rather?
Either Rather created the docs himself (I doubt it) or he knowingly used forged docs. The ONLY other possibility is that Dan Rather is so incompetent he couldn't spot the most obvious forgery possible.
CBS had been working on that story for five years. For five years they came up with nothing, because there was nothing. So with less than two months to go before the election, they were determined to run with the story. Since they didn't have any dirt, they created dirt.