Because of the collapse of CNN
The ‘rats jumped ship and now they are congregate over there
Not congregate....infest.
That was my first thought too. The lefties prefer hard-core impeachment porn. The relatively soft-core stuff peddled by CNN doesn’t quite do it for them.
You are right, the downfall of failed CNN has significantly aided the Maddow TV viewer numbers. However, her main draw of viewers comes from the Gay community many sectors.