>>281766307
Oda is literally a genius. Moria is around Oden's age in the flashback. The last generation of Kozukis who could read the stone was Oden's (so including Moria). And Kinemon and the others like the rest of Wano believed Moria vanished after Kaido fought him and considered him dead so they thought the art was lost with his and Oden's death.