my theory:Originally Posted by isso
Orocimaru used the mind transfering tehnic on third kazekage, thats how he got the sand armys rebelling in chuunin exams... it also explain that when one of the konoha jounin asked one of the sand jounins " is orochimaru behind this?", the sand jounin didn't know who was behind it...
The leader of Akatsuki is Kabuto(IMO)