That decline is only for the Tucker time slot. Overall the network is doing fine with American dumbasses who live and breathe political dogma. This is from a current Washington Post article:
"Fox still holds a commanding lead over the competition on MSNBC and CNN. And the network has weathered similar short-term declines in the past, including a minor dip after Bill O’Reilly was pushed out of the network in 2017. He was replaced by Carlson, who had the most-watched show in all of cable news in 2021 — eclipsing Sean Hannity, who earned that title between 2017 and 2020. The 5 p.m. panel show “The Five” was the network’s most-watched show in 2022, and it’s tracking that way again in 2023."
As for NewsMax killing Fox, not exactly:
"Viewership of Newsmax remains far below that of Fox News. But its audience at certain hours has doubled, and in some time slots tripled, in the immediate aftermath of Mr. Carlson’s exit — an abrupt spike that has turned heads in conservative circles and the cable news industry.
On Monday evening, Eric Bolling’s 8 p.m. Newsmax program drew 531,000 viewers, according to Nielsen. One week earlier, it had 146,000. On Tuesday, Mr. Bolling’s audience grew to 562,000 viewers, equal to about 80 percent of Anderson Cooper’s CNN viewership that evening. Newsmax’s other prime-time shows also experienced big jumps.
The sharp rise in viewership can be timed almost to the minute of Fox News’s announcement on Monday that it was parting ways with Mr. Carlson, in part because of private messages sent by the anchor that included offensive and crude remarks."
https://www.nytimes.com/2023/04/27/business/media/newsmax-fox-ratings-tucker-carlson.html