Well, we know why and how now, it was the 1954 picture of the military that started the lampost looking for the island and the Black Rock's Log that also had information to bring them there..
I still say the Dharma Initiative was a cover and I believe it has been show that in fact the DI was there to do what they said they were doing, but this the underlying knowledge as Dr. Candleman aka Chang, knew of "rules" and he either was obeying them or knew more about them.
Frankly there could have been an agreement with the others and allowing the DI to go there to do their research. So someone says okay folks you found us you are interetsted in the island "powers" and lets them go and do what they want with limitations.
Any of the Powers to be might have encountered issues with the others vice versa and thus the fence being put up etc.
But I digress Juliette should be sharing more than she is. She knows about the island, perhaps that is why they had counseling, due to the information that was shared.
Who knows, but frankly I also hope it is not anything lame like Atlantis.
Rambling sorry
