There are hints in Words of Radiance that the Thrill is tied to an individual entity that Taravangian has studied, possibly one of the Unmade. Does this have anything to do with the hints of why the Knights Radiant turned away? Were the Unmade some of those who did whatever-it-was that tore them apart?
Brandon Sanderson (paraphrased)
[This is the one where he stopped me partway through asking, probably due to the wording]. Does it have anything to do with it? Yes. Is it the root cause or the primary reason? I'm not going to reveal that right now.