1) Colbert: As we've established, Digg is populated primarily by young liberals; and young liberals love Stephen Colbert. (Mainly because young liberals hate Bill O'Reilly, and Colbert is the anti-O'Reilly.) The study in the article concludes favorably for fans of Colbert -- basically that conservatives just aren't smart enough to "get" Colbert. If the study hadn't concluded favorably for Colbert, surely the article would not have reached as high up on Digg.
2) Brevity: The study featured in the article was scientific, academic, and well-documented. This means that the article writer could have flooded his post with text and data to support the conclusion. However, he didn't do that; instead, the article is succinct and easy-to-read. It works much better that way for Digg.