[xxpor]

I believe a large part of the issue is that newspapers' neutrality has been part of their downfall, not their partisanship. Now it's easy to read something you always agree with. Local newspapers no longer have the captive audience of "this is the only paper that will deliver to your front door daily"

[weberc2]

I think it's slightly more nuanced; as the mainstream media moves to the left, the swath of views they fail to accurately represent grows larger (moderate conservatives and centrists, for example). Those whose views aren't being represented fairly are more likely to give up on MSM entirely and choose to support their own partisan media. This is all conjecture of course.