Forgot which part it was in the manga but if anyone has the time to look for it, please do so.
well, Kakuzu did mentioned that he was around during the time of Hashiramas reign.
So do you think theres a possibility that Kakuzu might have known that Obito wasn't really Madara?
As i recall, Kakuzu only stated that he's been around during Hashiramas time.
so maybe he's only been around when Madara left, therefore he hasn't met him.
that was my debunk. i guess i answered my own question but i'd love to hear other peoples opinions.