Uhhh. The "custodians" changed beginning in 1967. And there was quite a bit of political momentum to overcome.
ML/NJ
Actually, they didn’t. The Israel National Museum had custody of its intact scrolls, and the Ecole Biblique still had de facto control over the Rockefeller Museum’s trove of fragments, and Father DeVaux was not sharing or publishing. The contents of Cave IV finally saw the light of public scrutiny in 1992, I think.