User blog comment:12th Supernova/Chapter 820: Payback/@comment-4503935-20160316164302/@comment-24850639-20160316171531

Yeah, but unfortunately we won't know the man's motives until we get his backstory, which could be a while now. As far as the Raftel knowledge goes, we won't understand why the people who know refuse to tell anyone, until we know what that knowledge is. As of now my best bet is that whatever is on Raftel will give one immense power, and they're doing what they can to make sure it doesn't get into the wrong hands.

As far as the poneglyphs, maybe that's something that only gets passed to someone with Kozuki blood? It seems like the Kozuki's are the main family of the clan, but there's other families that support it to make up the clan, like Kin'emon and co. Momo may have been too young to learn?