Remember when I pointed out the Roderick Scott case?
All else being equal, if a story serves the liberal agenda, or at least does no damage to it, it makes news. Otherwise, no.
The Martin case made news because there was a Democratic narrative being served by it. Don't overlook the fact that some major players in the media made specific and deliberate efforts to falsify the facts to serve that narrative. That kind of thing is not about sales.
This isn't a conspiracy. This is a long-standing media culture. Chris Matthews is just the most obvious case.