Board Thread:General Discussion/@comment-24251492-20140105224559/@comment-26420452-20140106054534

Long ago, Uryū was claimed to be a genius by Mayuri because he'd mastered techniques other 4-5 times his age had not.

Yhwach acknowledges his potential because despite being Gemischt (mixed-blood), he survived the Auswählen. That is, when he was 9, he was as strong as an Echt (pure-blood) Quincy. He's continued training (at 15 he almost killed a captain of the Gotei 13) and upon joining the Wandenreich, apparently he performed a ritual with Yhwach that awakened his true powers. Imagine his current level...

However, he wasn't appointed as Yhwach's successor genuinely. Yhwach knew that this appointment would cause discontent and throw suspicion onto Uryū in such a way that would make it impossible for the latter to defect from the Wandenreich.