They believe there is a conspiracy to hide things there because the digging they are doing now has been minimized to protect the site from further damage.
Edit: The funny thing is that Karahan Tepe is probably significantly older, but they don't ever talk about it in their conspiracy theories.
Oh, but there's still evidence of the "great flood" because they claim there's evidence of that everywhere. But I don't think Corsetti is a creationist. He's one of the people whose concepts have descended from the extremely racist ideas of Madame Blavatsky (I'm not suggesting Corsetti is a racist, I'm saying that's where it all comes from) of an advanced civilization- often suggested to be Atlantis- that birthed every single ancient civilization after it collapsed regardless of the fact that the civilizations they claim all originated with Atlantis sometimes existed thousands of years apart.
As to why they are trying to hide it? According to Graham Hancock, who also peddles this nonsense, it's because the Archaeological establishment will all be embarrassed by being proven wrong. I don't pay enough attention to Corsetti's nonsense to know what his spurious reasoning is.