They're all culpable. They're all so terrified, and he's so vilified by them because he has absolutely zero need to settle out of court. His motivation is twofold; to protect Meghan and to expose their wrongdoing. If he wins, and the evidence he's presenting is the same evidence that has caused them all to settle out of court *hundreds* of time at a total cost of more than £1bn, then their whole existence is threatened. All their previous defences of 'nothing to see here', 'nothing proven in court', 'just doing our job', 'in the public interest', 'nothing illegal'; all of this is absolute crap. They operate above the law, in their own interest and only in their own interest.
To understand their behaviour, think of when a narcissist is called out on their behaviour and how they react. Only this time the person calling them out will not back down, will not be intimidated and will pursue and expose them to his last breath.
The press see his actions as an existential threat. And they are right to.