User blog:Dettles/Why didn't Marco protect whitebeard's terrorities?

After Whitebeard's death why did the Whitebeard pirates lost all their terrorties? Marco, Juzu, and Vista are all strong enough to protect the Islands. Why did Big Mom take Fishman Island; I thought Blackbeard took Whitebeard's terrories? Wonder if the whitebeards pirates will come back to the story?