I have read the book written by Boris Kuznetsov, a russian lawyer who represented the families of sailors killed in the submarine.
According to the book the files of ctiminal investigation were fabricated by russian authorities to release from criminal prosecution the high command of the fleet.
Kuznetsov had to remove to USA to escape from the harassment of russian government agencies.
https://en.m.wikipedia.org/wiki/Bori...etsov_(lawyer)