It was the texts.

 

On Eve of Trial, Discovery of Carlson Texts Set

Off Crisis Atop Fox

 

There were redacted texts that were never made public that Fox' lawyers had but Murdoch & Son didn't see until the day before the Dominion trial was to start. "Two days after the board’s discovery, Fox settled that case for $787.5 million, believed to be the highest for a defamation trial." NYT, AP, and NPR have "challenged" the decision to keep the redacted texts from the public.