Everyone has a worldview. It’s the framework through which you understand the world, and into which you assimilate new knowledge. One worldview can be more accurate than another (modern scientific rationality versus all previous worldviews for example), but it’s also common for two worldviews to each get different things right and wrong (classical Mayans knowing more about astronomy but less about metallurgy than Europeans for example). If everyone you hang around with has a basically similar worldview to yours, it doesn’t really even seem like a worldview at all; it’s just the way the world works.
That’s what has happened to the mainstream media and to the people who get their news exclusively from it. The mainstream media (Network news, CNN, NBC, New York Times, Washington Post, etc.) all reflect the same basic liberal corporate centrist worldview (left neoliberalism). The last few decades have seen the rise of another popular media worldview: the conservative corporate hard-right worldview (right neoliberalism) pushed by Fox News and the rest of the Murdoch media empire. And more recently we have seen the rise of the internet creating opportunities for a lot more media worldviews, primarily the too-racist-for-Fox alt-right worldview and the whole gamut of possibilities to the left of the mainstream that had previously been shut out of the conversation.
To people who still exist purely within the mainstream media worldview this looks like everybody who is exiting that worldview is just going crazy. They’re starting to have beliefs that the mainstream media worldview says are incorrect. It leads them to talk about a “post-truth” world and fret about how we can’t agree on facts anymore. What they’re missing is that there was never an agreement on the facts, just a situation where the media was united around one interpretation. Meanwhile the people exiting that worldview to the new alternatives feel like they’re waking up to the mainstream media’s lies and have now found the truth. To be fair to the exiters, the mainstream media worldview is very flawed. To be fair to the mainstream media, most of the alternative worldviews people are leaving for are at least as flawed, often way more.
We’re going to have to get used to a world where people choose media sources based on agreement with their worldview. Other sources feel like they’re lying to you by reporting based on assumptions you don’t share. People who agree with the mainstream media worldview are bummed that everyone’s no longer forced to hear reporting from their perspective, but the rest of us will be able to hear reporting from a perspective we share. And that’s not so bad.