As someone who worked at one of the large networks, I disagree with you when you state that it was more of an HR than PR thing.
I can assure you the types of behavior that these male actors were accused of were no secrets, neither at my company nor in the industry. Nobody did anything about it, and it wasn’t until it blew up into a fire storm thanks to social media that these companies decided the best response from a business sense was to suddenly pretend we are on a moral high ground and sever these relationships. It was fear and about saving image.
Otherwise, the response would have been to deny and secretly pay off accusers while maintaining relationships with the Kevin Spaceys of the world.