I'm still going with the idea that Syl could possibly be the dark mastermind behind it all. Derek seems to have a very clear idea of the situation, while the prince seems to have no recollection of that, only "remembering" his dislike for Octavia. It seems weird to me how disconnected both Derek and the prince are.
What's more, the King seems to have had his own suspicions, and confronted Octavia about the situation, since he probably knows about the attacks. The King seems more reserved however, suspecting something else at play besides his daughter's attempt to overthrow him and his heir.
This seems so oddly political when you compare to the FL views of things.