User blog comment:Fliu/Chapter 947: A Small Step Forward and a Lucky Break/@comment-25654036-20190628134149/@comment-2600:6C5D:5D00:1C9:51C6:B69C:7FB0:7668-20190702043828

Only Blackbeard and Sanji have detailed knowledge about the various Devil Fruit that were studied and cataloged, so unless they truly believed that devil fruit are real and have access to the encyclopedia, they can try to be lucky in finding the specific fruit they want. Blackbeard only joined the Whitebeard pirates and not made a name for himself is because he is patient and believed his luck in finding the Dark-Dark Fruit would increase. Doflamingo and Tesoro kept a close eye on underworld auctions on certain Devil Fruit.