As a big fan of conservative talk radio - I'll do my best to hypothesize objectively
Ratings are done by surveying the market twice a year, in the spring and the fall. The surveys are sent out to a sample audience in each demographic, and those people selected indicate what they listen to when, then Arbitron compiles the data and you have ratings. In short - it's a not a very good system (or accurate), but it's what we have (TV's the same way with Nielson), that's why most broadcasters and agencies refer to how a station performed over four ratings periods to create an average, as opposed to just referring to performance in one book. KFQD, for instance, has some great books and some average books, their average indicates that KFQD has a strong presence in the market - a 'bad book' for KFQD can most likely be attributed to diary placement in the sample audiences. KUDO has not ever performed well - which is consistent with the national trend for stations like it. I'm always surprised by how many people call in too, and apparently some of them are getting diaries, hence their 1.0 share that they've achieved for at least 2 of the last 4 books, I'd be comfortable saying that's an accurate representation of that station's reach.
My therioes as to why are that Anchorage and Alaska in general are predominately conservative markets - and conservative talk radio has always done fairly well here. The 'Liberal Left' is fairly over-represented in the form of NPR, newspaper, local and network TV news, and right here on the internet with online news, blogging, etc. While KUDO fills a niche (and good on them for doing it), it's a viewpoint that's not very well served on talk radio.
...As an aside - I would never waste a moment of my time listening to a mental midget like Aaron Selbig or chronie Allen Tesche...shame on both of them for taking a personal call (however unethical) and trying to capitalize on it. If they were actually trying to do the right thing - Tesche and his wife were in a position to filter that through the appropriate channels and Coffey/Starr should have been punished accordingly - if what they 'did' was actionable. That, KUDO is why myself and people like me ("right-wing nut jobs") will never listen to your station or knowingly support any of your advertisers.