I hadn't thought to connect it to the death of Honor, but that might make sense, especially if the Bondsmiths were bonded to spren directly related to Honor, like the Stormfather (or even to Honor himself?).
I'm inclined agree that they had to have rationalized it somehow. It seems unlikely (and terrifying) that they might have all suddenly decided their oaths were worthless simultaneously. How they rationalized is the question, and I think a key factor is whether they knew that breaking their oaths and stepping away from their Orders would kill their spren? If so, why did they do it anyway? Were the spren involved in the decision, or were they tossed aside? Did the spren know they would die?
It's possible it's something inherent to the way in which the humans and spren are bonded. If, for instance, the KR tended to take their powers for granted and take advantage of their spren, it might lead them to stop listening to their spren, who provide reminders of their oaths. And, as we've already seen, this kills the spren. More to the point, we've already seen even Kaladin taking his powers for granted and starting to take advantage of Syl.
Certainly, the spren left in the Cognitive Realm, and the Stormfather especially, are under the impression that it is the natural course of the bond that it will eventually end in betrayal. So I wonder what they know that we don't, and did they have the same opinion of what was happening on Roshar around the time of the Recreance as the spren bonded to Radiants had?
I hope it's something like that, and not something more nefarious. This is a plausible possibility, though I'm not convinced the spren would necessarily consider that a betrayal; I'd almost be inclined to think at least some of them might consider it worth dying to try to avert petty wars among various kings, etc.