Something not mentioned much is the fact that the area was put on lockdown for 3 years after the tragedy. This must form part of any investigation and all theories must take this into account. What happened that was so bad that the area had to be put out of bounds for 3 years ! ?
Mr. Vladimir (WAB) said, that this "lockdown" as well as the "25 years of non-disclosure" are parts of a widespread myth.
He himself interrogated many of the search teams members (such as Bartolomey, Karelin, Brusnitsin, Slobtsov, Sharavin, Mohov, Askinadzi, Koptelov), as well as Yury Yudin. Non of them mentioned anything about that.
The "lockdown" was in regard to forbid to officially direct hikers. As far as I got it, It means, that you cant go there in order to obtain higher sports degree and have official documents for it (what the Dyatlov group was trying). Anyone who wanted to go to the area was free to do it, just without the official registration. From March till September 1959 there were groups who went on a hike.
As WAB said, you cant just "close" a wilderness area with the size of Belgium for years.