Ok... A simple theory...
The war was a memory, cultivated while Xehanort was sleeping. In it, we saw his dream just like he did. When it ended, he woke up (in the past) and thought of a way to bring himself back to life for the future. His answer, CHASERS!! He became a chaser, and equipped with the power to control other chasers, he waited for the future to get even with the Keyblade Master (currently Sora).
It's wrong, but could spring controversy.
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