there's zero evidence of any blast shock and the autopsies don't evidence it
True. On the contrary, there is a lot of evidence of thick snow on the spot. Thus we come to the theory of a snow cave in the ravine and its collapse.
At the same time we have Ivanov's very direct statement in the newspaper article:
"The true causes of the deaths were hidden from the people, and only a few knew these reasons: the former first secretary of the regional committee A.P. Kirilenko, the second secretary of the regional committee A.F. Eshtokin, the regional prosecutor N. I. Klimov and the author of these lines, who were investigating the case".Trying to match this statement with the Snow Cave theory we may conclude that Kirilenko, Eshtokin, Klinov, and Ivanov knew about the snow cave in the ravine, while Maslennikov, Tempalov, Askinadzi and all other people did not. Though Kirilenko, Eshtokin, Klinov had never seen the ravine... For me it sounds absurd. As for Ivanov, knowing about the snow cave, he was expected to start studying special literature on snow traumas, but he preferred to hunt fireballs and order radiactivity tests.
However, if we admit rocket collapse nearby and further blast of its fuel evaporation, that was class of events regional leaders would have been informed by federal authorities. The logic is back - those, who were entitled to know federal secrets, knew the truth.