Mysterious cave / vault 79

Can someone explain this whole thing to me? I finished wastelanders and did vault 79 with the settlers. I know the Raiders enter the vault by blowing up the main entrance and Settlers drill in through the side. After that I decided to do the grafton pawn shop unmarked quest and got all the map fragments and entered the cave elevator. There's nothing in there except the vault entrance, right? Is there a point to the quest if you go with the settlers? Is the unmarked quest required if you side with the Raiders?