The Aiel are and always have been some sort of monstrous aberration. What other ethnic group requires a unifying purpose, as the Aiel always have? In order for them to give up this need for a collective purpose, they must be broke so there can be no hope for the remnant of a remnant to be useful, and instead, they can just get on with being people who lead their own lives, whether ordinary or normal or heroic or evil, just like everyone else. They need to be shattered like Manetheren so that they can be real and normal people like Rand & the other Two Rivers characters. Manetheren lasting as a mighty nation might have given Rand an entirely different sort of upbringing, whether his adoptive father was a mere common soldier returning to his farm, or a noble-born warrior and officer who raised his adopted son and possible heir to be a lord and leader. More likely, had Manetheren lasted, their heroic qualities would have been degraded and lost as they took a bigger role on the world stage or something. The remnant of a remnant, however, was able to preserve those heroic values and virtues that made Manetheren great and pass them on to the three ta'veren who would be required to save the world one day. Thus as well, should happen for the Aiel. Greatness destroyed Rome and the old Roman people, values and traditions. Destruction saved Manetheren's people and values and may do the same to the Aiel. Captivity in Babylon preserved the Hebrew traditions and customs and taught them to value what they had lost, while their brief experience as a great nation corrupted even men chosen by God like Saul, David and Solomon. I think this is the necessity the Aiel will have to face.