I couldn't fully see what was posted in the article since it was wanting me to sign in or something, but I will assume that it was showing Fox had a larger market share than the alternatives.
The reason why is NBC, CNN, MSNBC, ABC, etc are far more in competition with each other than Fox is with them. There are no major right of center competitors to Fox. This results in most right of center tv news watchers going with Fox. If there was only one left of center news channel Fox would closer to even with it.
[1] https://www.statista.com/statistics/373814/cable-news-networ...