TV ratings matter immensely for network television because advertisers are looking to sell products to viewers.
For cable news programs, the ratings alone don't matter because the big advertisers aren't selling directly to viewers. Nobody buys Pfizer products, for example, just because they advertise on Fox News.
Instead, major corporations advertise on cable news shows to pay the network to peddle the company's propaganda. So Fox News takes ad money from Pfizer, and in exchange, they get their hosts to promote COVID vaccines (or at least not to talk about the adverse effects). Boeing pays ad money to Fox, and in exchange, the company's paid b!tch Lindsey Graham has an open invitation to go on any show and promote endless military campaigns all over the globe. You get the idea.
Tucker Carlson didn’t have major national companies sponsoring his show because he wasn’t willing to toe the line and spout their bullsh!t on the air. Frankly, this made it much easier for Fox News to cut him loose.
It’s not the number of people that watch the show, it is that the people watching are of desirable age and income groups.
You are not going to sell a 72 year old man tampons and are not going to sell at 22 year old a reverse mortgage.
I understand about viewership not equating to advertising, if it did CNN would be bankrupt because no one watches them