If I were a board member of any of the major publicly owned media companies, I would take note of the increasingly strident tone of his tweets, especially knowing that Trump does not pull punches when fighting back. He probably has the information that he needs about the coordination between IC and specific journalists.
The board members now need to look at whether Trump will look at the media companies in the way that the Feds looked at Arthur Andersen or how they looked at Wells Fargo. Both of those cases involved employees who engaged in illegal/unethical conduct. Difference is that in one, the government decided to file charges against the company and not only the individuals. All they need to show is that if there was unorthodox cooperation, it extended beyond a single journalist.