It’s a lot simpler and straightforward to me.
The media (or at least 90% of it’s individual members in 2020) are hard-core Socialism fans. They are rooting for Bernie, the Fake Indian, or somebody just like them to assume the reins of power. Thus all old-school “centrists” like Biden must be kicked to the curb in order to clear the rails. Now that they don’t have the shiny object of impeachment to distract them they are going to set about the task they believe is their birthright (that being choosing the Democrat nominee).
He’s not a centrist. He’s a leftist. The problem is, the far left in the party have made it so insane that they make him look almost conservative by comparison.