Conversion to what exactly? The Novus Ordo religion? So in actuality an apostasy.
Did Mary promise apostasy (utter abandonment of Christ)as a reward for the Nope fulfilling his duty to conform to her request? Makes no sense.
You forget about the chastisement predicted in supressed part of the Third Secret and by Our Lady in Akita, as well as numerous other prophecies of chastisement, perhaps Three Days of Darkness - after which there will be a restoration and then Russia can certainly be converted.
By the way they are right in saying the consecration, post failure to do so in due time, would not have required the comparticipation of all bishops etc.
That was only for a hypothetical valid one which would have also avoided WW2 and Russia's errors spreading, war, famine, etc.
How does that follow from any part of Fatima apparitions or later words of Our Lord and Our Lady to Sr Lucia? We know that the consecration will eventually happen, but it will be late (Our Lord clearly say "they will do it", which implies a valid consecration with every bishop).
Also, taking "a period of peace" to mean absolutely global absence of any conflict whatsoever is unfounded, and impossible given Man's Free Will.
What we have been dealing with since 1952 (allegedly final Consecration, according to the Dimonds) are not merely some local conflicts, but major conflicts including greatest world powers (Vietnam, Iraq, two invasions of Afghanistan - by Soviets and Americans), accompanied by incredibly bloody local conflicts (Yugoslavian wars, Nagorno-Karabakh war, numerous wars in Africa - including Rwanda genocide). This was not a period of peace in any way, shape or form. Also, despite human free will God can intervene to bring about His promises.
Thirdly, they do not merely consider "conversion of Russia" as "conversion to peace", but the gradual abandonment of Communism, and in particular Stalinism and annexed persecutions of the faithful.
This is exactly what I called grasping at straws in trying to reconcile Fatima with sedevacantism and Dimonds' interpretation of Revelation and Malachy's Prophecy. When Our Lady spoke about conversion in previous Marian apparitions, it was conversion to the Catholic faith (like in the case of Mexican Indians) - nothing indicates She meant something else here.
Also, to suggest that fall of communism is conversion seems extremely unlikely - the fall of communism was certainly (at least to certain degree) a plot of high ranked communists who wanted to change the economical system to lay their hands down on huge money while this change was happening. Also, in current Russia rates of abortion (highest in the world), alcoholism, spread of pornography and other abominations, together with involvment in military conflicts make any claims about Russia's supposed "conversion" absolutely ludicurous.
Honestly it seems manifest to me Fatima's potential as a Panacea for all the world's (and Counter-Church's) ills is wishful thinking more than anything harbored in reality.
Sorry, but I take that as lack of faith in divine promises. Also, no one says that Novus Ordo will necessarily return to Catholicism immediately after Consecration of Russia - given the situation and other private revelations it is more probable that the Consecration will be done after the chastisement which will sweep away the Novus Ordo (I hope I'm wrong on that, though).
Objectively speaking, given all the confusion and naught regarding Fatima and the Secrets, including but not limited to the Fake Sr. Lucia and subsequent interviews, books, etc, and even a Fake Third Secret manufactured by the Vatican, how could one even expect to dogmatically rely on it?
First of all, there was no "fake Third Secret manufactured by Vatican". Everyone agrees that the vision of bishop in white is authentic. What Vatican did was not manufacturing, but hiding part of the Third Secret.
Also, I don't think there is as much confusion as you claim - it is a well-established fact that there is another text which was covered-up and and we have enough evidence to get a pretty good idea what it contains (warning about apostasy in the Church and some sort of material chastisement).