Yeah Manga is funny that way. If I were KUBO, I would spin in that Isshin was Under Orders from Squad Zero not to intervene, and Only Urahara, Yoruichi, and Yamamoto Genrusai, knew of the orders, but they didn't know why or anything else.
Originally Posted by Gaara Kazekage
Maybe Squad Zero has a See'er who fortold these events and Orderd Yama-Ji to not directly interfere with Ichigo.
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Growing Old Gracefully is an Oxymoron ... Mostly Moron !