The point isn't that he was outed as only a scapegoat. The point is why you'd spend time waiting to see who you should fire before letting your victims know.
It's not like Dara walked into a whiteboard in the CEO office that said "list of 2016 suckers lol" and then sat on it twiddling his thumbs for a month. My understanding of the incident is that it had been covered up by Sullivan and TK. In my mind, an investigation is precisely for figuring out what the hell happened, who was affected and to what extent.
I don't know the specific details of this investigation in particular, but for the Holden one, it involved a lot of one-on-one interviews with various employees to try to reconstruct the stories of each harassment claim so that an appropriate punishment/course of action could be determined for each case. If this investigation was conducted in a similar manner, it wouldn't surprise me that finding out the blame would occur in tandem with discovering the extent of the breach.
