As I recall, this all started with a Hannibal Burris comedy bit where he's taking Bill Cosby to task for something he said and basically ends the bit by saying, "Well Bill Cosby, you rape women, so shut the fuck up!", or something similar. I don't remember the setup for the comment.
I remember he's been doing the bit for a while, and have heard it several times, but a video of it recently went viral and that prompted the women to "come out of the woodwork". Or more likely promoted a journalist to investigate the prior claims, and that started this snowball. But we won't know that for sure unless someone pushes the original woman who came forward for what prompted her to come forward now.