We know that Radiants broke oath and killed sprens.
How come all of them did it at once?
Wasn't there trial and error to check the consequences ?
Radiant are all over Roshar, how did they manage to inform this to each and every Radiant
Was there an annual gathering of Radiants where they did this ritual?
How come none of them denied/accidently survived by lack of communication?
Also, the way different Radiants break oath seems different for each Radiant
Jasna is OK to kill the Harards and nothing happens to her Spren
Whereas Kalidan helped to kill Elohkar and He almost killed Syl
Then how all the ancient Radiants managed to break oaths at the same time ?