Those recordings are of interviews with a couple of *rump people, no private recordings of Tucker.
According to Marcy Wheeler (aka emptywheel @ https://www.emptywheel.net
) the Fox lawyers went through a boat load of digital recordings, emails, text messages, etc and uncovered an overwhelming amount of evidence that implicates Tucker and his executive producer (Justin Wells - who also got canned) over statements that Fox can no longer sustain or defend. It could be his attempts to get cozy with Putin that NSA has been monitoring since 2019. It could be what he has said about the top brass that is un-nerving. What ever the case, when your employer does a surveillance of your communications, you may be in big trouble.