But the Germans were only digging in the wrong place because Indy got the headpiece from Marian, leaving them only half. If he hadn't, they would have gotten it and been digging in the right place all along. Which I think BB mentioned. Would Belloq have delivered it to Hitler or opened it himself as he did in the movie?
good point about the amulet. Without Indy they would have got a whole amulet and story over.
And no way Belloq would let Hitler have the Ark first. he even states as much.
Without Indy, the Ark would have been abandoned on a Nazi-controlled Greek isle waiting for a fresh submarnie to dock there and pick it up.