I suspect it's more because conservative views have long been an underserviced market (whereas much of the mainstream media tilts left - and quite openly so as per pew poll performed annually if I recall: http://www.npr.org/templates/story/story.php?storyId=1919999).
How does the "Mainstream Media" tilt left when
1) Fox News is a member of the MSM. It's not an underdog either: it's an industry leader. The highest rated cable news network, by far, is Fox News, often beating MSNBC+CNN combined- unless there's a rare event like the recent earthquake, at which point CNN only slightly trails Fox.
2) The allegedly liberal New York Times and NPR refuse to use words like "torture" because, according to their editors, "torture" is too political of a word, and instead use the newspeakesque "Enhanced Interrogation Techniques".
3) The media's wholesale embrace of the Iraq war in 2002/2003/2004, before it became unquestionably a quagmire 2005. This was true for even the New York Times, which basically gave the Iraq War the Grey Lady's stamp of approval.
4) Most newspaper Op-Eds are conservative, even in local papers that have no national coverage.
5) The largest Newspaper in circulation ATM is the Wall Street Journal, another conservative paper owned by News Corp.
6) Advancement of the "Real American" narrative which states that those who do not appreciate people like Sarah Palin aren't "Real Americans". Coincidentally women and minorities don't like Sarah Palin, but I'm sure this was in no way a slight against those people but instead the invisible "elites" who apparently ruin everything for everyone ever in the realm of politics.
The fact of the matter is, most of this so-called "liberal" media are really just star-fuckers, who enjoy bootlicking those in power. Today, it's the Democrats, yesterday it was the Republicans.
Here's a good example of what I'm talking about: "...everybody sort of likes the president, except for the real whack-jobs..." -- Chris Mathews, on Hardball, November 28th 2005.
From the same guy who gets tingly about Barack Obama.
Personally I'm not entirely convinced that NPR necessarily tilts left as there was a study conducted a number of years ago that suggested they were actually fairly close to center based on the sources they used in their reporting. Fox apparently only tilts slightly right, and WSJ's news pages actually tilted slightly left.
For Fox News, their rise has only been relatively recent. CNN's massive fall has only been in the last couple years. Further, I would also suggest that the reason WSJ has been so successful is that markets depend on accurate information - and in this, removing bias in favor of details and content is important given their audience makes money on both sides of a trade. Whereas you might say New York Times' aims to influence decision makers, WSJ would attempt to inform them. Of course their editorials tend libertarian/conservative and quite openly so. I completely disagree that most newspaper op-eds tend conservative - particularly given it's the editors themselves who declare themselves as liberal.
However, getting away from bias from a moment, whatever you may think, unabashedly conservative talk radio has found success specifically because it found a rather large underserviced niche. If to you, this means that these people are extremist right wingers is irrelevant. Both the quickly growing audience base of Fox and conservative talk radio (and the failure of Air America) reflect the reality that there was a market that was largely underserviced - and that Air America did not meet that need - despite their medium. It was their underlying message/content that did not resonate.
There's a lesson there, politics aside. (cough Y chromosomes are not a pre-requisite for using software. cough)