I don’t think ratings matter to them.
As a cable channel they get small piece of the pie even if no-one is watching.
I don’t know the particulars with CNN but I do know a lot of low performing channels are bundled together and sold to the cable companies as a package. Usually there is on channel their subscribers really want, the rest are losers. But to get the one channel they must take all of them.
The cable companies do not really care either, they are like a casino, they get the house cut (passing on all expensive on to their subscribers)
It is time that the courts do to cable companies what they did to Ma Bell. Break them up, allow any cable company to use the wire to the home.
Allow customers to only pay for those channels they want.
At Dish Network, if you get the least expensive package, the only news channel if Fox News (little secret)