>>93136158Time is slow at correcting paradoxes. It started erasing the future immediately after Aku's defeat and then slowly erased everything onwards. It just took that long for time to catch up to the far future results of Aku's reign and erase them. The very last things erased were Jack's memories of the future, which is why you see him smiling at the end of the series; it was at that point he forgot Ashi and his whole adventure and thus no longer had anything to be sad about.
