Mark, even if we take the Armenian “SSR” as typical of the Soviet Union as a whole (can we?), judging the ideological state of the Soviet Union by what people believed in the mid-1980s is like judging someone’s overall intelligence on the basis of the years of his senility.
I don’t think that it is possible to deny (and I don’t think that you do) that there was a real, and successfully, implanted religious (or-quasi religious) feeling among the many communist believers through much of the Soviet period. As for the iconography of this religion, whether it was Lenin’s tomb (still attracting the faithful when I first went to the USSR), the military parades through Red Square (you can trace their format back to Byzantium) or the scenes of hysteria at Stalin’s funeral, I think it quite clearly ‘took’. And there are many, many other examples.
As to when that faith died, it was probably some time in the ‘stagnation years’ of the Brezhnev era. As to why it died, that’s complicated, but a combination of growing systemic failure and a much more highly educated population were important elements in its decay.