https://www.yahoo.com/entertainment/msnbc-chris-matthews-accused-inappropriately-221533235.html
This is happening to him now because of his recent comments strongly denouncing Communism, Socialism, and Bernie Sanders. They're taking him out long before the election, now that it's nearly certain that Bernie will be the Democrat nominee.
They're for whoever gets the nomination, and they're for Marxism (though they prefer doing it gradually undercover rather than out in the open).
They don't want Bernie to get the nomination because he's the most likely to lose. But now they can see that he will be getting the nomination.