I think death is not the only factor. The tests were conducted in an open area, the territory of Novaya Zemlya still has an elevated radiation background, and the winds bring it all to Western Siberia and the Urals. People live there, and if government disclose the information, they will have to pay compensation, which is a very decent amount of money. You may also have to disclose the location of active bases. Military secrecy is a case where what seems like a trifle can actually have huge consequences and it is easier to hide everything.
In any case, it has little to do with the incident, since herd of reindeer might have been spooked by something other than a rocket, or they might have just been wandering the usual road for no reason. The theory as a whole may be wrong, but the important fact is that there are even several scientific versions. This should put those who talk with a serious face about Yeti and UFOs in their place.
A local guide told me one of the scientific versions, which is common among local experts. It is quite simple: the missile test scared a herd of reindeer and they ran along a path known to them, which passed through the tent. The Russian authorities even now cannot disclose information about the tests, because those who launched the missiles are still alive and have high ranks (and if the information is disclosed, these military personnel would have to be jailed for causing death by negligence). The Mansi wouldn't tell about the reindeer because they were afraid they would be exterminated. That's where the science ends, the rest is just the tour guide's thoughts.
Also, the tour guide said that Dyatlov's group was not an exploratory group, but just a few students going on a hike. It was known about the snowstorm in advance, but for some reason it was still decided to go on, rather than wait out the good weather. Another important factor was that the group had left warm clothes for the return trip, so those who got out of the tent just froze.
Sorry if there are mistakes, I used DeepL.
In any case, it has little to do with the incident, since herd of reindeer might have been spooked by something other than a rocket, or they might have just been wandering the usual road for no reason. The theory as a whole may be wrong, but the important fact is that there are even several scientific versions. This should put those who talk with a serious face about Yeti and UFOs in their place.