Have you ever been involved in any Court Case in a Court Of Law ? All the evidence is presented and the outline of the known events and then you get cracking on trying to solve the Case.
Yes, I have been present in two long court cases. But these cases were not about homicide.
We are however not close to a court case here. Before a trial, evidence has to be produced.
I assure you, the first thing that has to be done of a corpse (or several) are found is to ascertain the cause of death. That is how investigation starts, in order to find evidence.
Investigators do not ask whether there is an obvious motive for murder, and then conclude that the death(s) are natural unless there is an obvioius motive.
They start with a thorough examination of the dead person(s), with the purpose of finding the exact cause of death.
In this case, that was not done. On the contrary, there were orders from Moscow that the investigation must conclude that the Dyatlov group perished from an accident. But that was not the case.