It's actually because of geography and demographics.
I lived out in the country for most of my life, around hunters, fishermen, farmers and campers.
Even today and especially back then you couldn't really get reliable cable or satellite. You pretty much had two or three channels (the only televised news we had was local). Growing up if we wanted world news or even national news we generally had to turn on the radio.
Now, it is no secret the Conservatives have strongholds in rural areas like where I grew up.
The hunters, fishermen, campers and farmers are rural types, and other than the paper and radio their links to the world are few.
Liberal Talk Radio is unpopular not because it falls on its face, but because in rural communities Radio still holds a significant portion of the population who rely on it for their national and world news.
You're not going to make money selling tank tops to the Inuit. Know your customer base-that's key in business.
Now onto your second question, which is actually related to the first.
The issue as I pointed out above has nothing to do with content and all about the demographics of listeners.
Because Radio holds sway in Rural areas, Urban areas (which are largely Liberal, again-no secret there) has a Cable and Satellite Dominance. This means that Conservative channels will be few. However, it is wrong to say that Rural areas are 100% Conservative of that Urban areas are 100% Liberal.
Since there is only one major Conservative channel, it's natural that this channel is going to be what Conservatives all watch, therefore-if there were only two channels, one Liberal and one Conservative, the Liberal one would actually have more viewers simply by demographics.
It has nothing to do with quality of content in either respect.