The difference here is all the attempts at Oak Island, including the first discovery of the pit in the early 1795 had multiple witnesses and were fully documented thereafter. And it is not as simple as "well someone found it earlier and filled it back in", because if that was the case then all of the depth marker platforms would not be there.
Sorry if I seem a bit passionate but I have been fascinated by Oak Island ever since I read a book about it as a teenager. The most interesting thing I find is even with all the technology and engineering prowess available today, there is still not a way to just dig this hole up. For example, these guys on this show have literally spend millions of dollars on this - and they are engineers trained in deep well drilling - and they are still no further ahead. Tens of millions have been spent over the past 100 years trying to dig up this hole and deal with the spillway booby-trap.