It's been trending that way for awhile now. It's largely becoming urban vs. rural/suburban.
It might have been the same podcast (maybe with Theo Von where they said it?) but he also mentioned that the cities are all in a trance. A leftist trance, to be specific. All of us have known this for years but I was glad to hear someone like him finally come out and say it. He also made the connection with universities and their proximity to cities and them being a large reason why so many people in urban areas are left leaning.
They aren't "educated" people, per se. They are indoctrinated and are told they are the smartest people in the room by their commie professors.
The other major reason is ethnic minorities like blacks are focused in the inner cities and have been voting left for decades due to the Dems promises of free shit.