Russia is a very interesting case IMHO. They obviously prefer dictatorial/autocratic government culturally. I don't say this to bash Russians, because I worship with Russians. They have a very positive view of their Tsars (to them it is a golden age), and even Stalin has had a resurgence in popularity.
I honestly think a fascist USSR would bode to last much longer than the Socialist one (provided we actually get PODs between 1918-1930 to both keep NEP going and Soviet support for the Church.) Russia has arguably drifted into fascism today under Putin, so just imagine a Russian government that is largely the same ATL, perhaps with a little less democratic elements.
In 2012, if the former USSR still existed, their population would be
298 million. This is with the Ukrainian genocide, WW2, NEP, legalized abortion, forced urbanization (urbanization ALWAYS decreases birth rates) and etcetera.
A present-day ATL USSR would easily have 400 million people. Due to fascism, we would be dealing with a lot of these people being converted over to Orthodoxy over the 20th century.
We then also have a fascist Greece, fascist Bulgaria, fascist Yugoslavia, Fascist Romania... Czeckoslovakia would be in this weird middle ground, though I bet they would actually be within the sphere of influence of the "second world." I think we are too quick to think a West always wins sort of thing. IOTL,
the USSR accounted for 20% of the global economy and the USA 28%. This was AFTER famines, demographic disaster, their industrial base literally being looted..etcetera. So, it does not take some huge stretch of the imagination that the USSR ATL would perhaps even
exceed the US, though certainly not per capita and they would be significantly behind the first world as a whole (French Empire, British Empire, etcetera.) Nevertheless, can Russia exert enough influence to
Finlandize Sweden, Norway, Czeckolovakia, Hungary? Easily.
Real knock on effects can occur depending upon which loony takes power in Germany. A Fascist USSR definitely butterflies away the Nazis...but it does not make a France-Germany rematch impossible. At the very least, during Germany's build up, they will become a key trading partner for the USSR. If Germany fights, the USSR might very well annex parts of Germany (which will inflate their GDP and improve their export capacity and intellectual capital.) At the very least, they would be given in trade tons of German technology and Germany proves to be a significant buffer state between them and the West. In all liklihood, Germany is fascist and is an ATL Yugoslavia...not under the SOviet thumb, but not under the West either.
Japan's role in this world is also interesting. They are in collision course with someone...and it won't be Russia. And, whichever western power they end up dragging into war, they will end up being beaten and ironically, the USSR will end up occupying before the last bell all the best parts of the Japanese Empire (Manchuria and Korea) while the Wallies would have fought the war for POS islands and Southeast Asia. Talk about the short end of the stick. ATL Japan may or may not actually be occupied by Western powers...my guess is that they will not, as the Nuclear bomb will be invented by the Germans or British first...not the Americans. Hence, the peace will be struck after starvation and massive level bombings, but not a full blown occupation IMHO. If Downfall does occur, this only strengthens Soviet influence post-war. After the War, Japan will be a Western satellite.
THis means the USSR will be propping up fascist forces in China while the West will be propping up some group that is behind the Emperor or something. Being that the USSR is on the ground, they probably win and not the West. China becomes a fascist ATL version of themselves. In fact, decolonization will have a totally different flavor. It will be unabashedly nationalistic and fascistic, while the West would be intellectually contradictory (propping up dictators to keep up their imperial empires.)
On this note, I think Korea, Manchuria, and Northern Japan pose absolutely fantastic evangelistic opportunities for global Orthodoxy ITTL. South Korea today has a huge Presbyterian population due to their country being rebuilt with the help of Western missionaries. Well, the liberators ITTL of a much larger stretch of Asia will be the USSR. They will be bringing with them Orthodoxy, which already had tiny footholds in China and Japan IOTL. After harsh Japanese occupation, Soviet liberation may provide a pretext for an ATL mass conversion to Orthodox Christianity. This alone may increase global Orthodoxy by about 100 million...maybe more. This also has interesting knock-on effects for global evangelism. Orthodoxy will definitely be viewed as a multi-ethnic religion instead of a Greek/Slavic form of Roman Catholicism as it is today. Also, these Asian churches would at the very least be autonomous by now, though I seriously doubt they would have autocephaly (again USSR is fascist and will have a lot of control over the Moscow Church.)
Ecumenical dialogue is something that may prove to be interesting. IOTL, quibbling over transubstantiation with the Anglicans might lessen, though union would NEVER happen. A coup might be pulled off in Nordic countries and the state Lutheran churches might be converted to Orthodoxy and their Bishops re-ordained (I do not think
economia would be used simply to turn them Orthodox with a stroke of a pen.) Anglican and Roman Catholic countries during de-colonization also come into play, especially if Soviet weapons and finances back those who overthrow Western Imperialists. It is not impossible, in some limited circumstances, that the nations Bishops in a show of nationalism convert to Orthodoxy and bring their flocks with them.
Things are not all rosey for global Orthodoxy ITTL IMHO. Even if their numbers are huge (500 million to perhaps 700 million if everything goes right in Asia and Africa), there is going to be
massive internal strife. Obviously, ITTL the Moscow Church has the most power de facto, but all the power de jure belongs to Constantinople, Antioch, Alexandria, and Jerusalem. ITTL, the Moscow Church is probably going to being stealing Asian Christians from Antioch (theoretically this is their jurisdiction) and African Christians from Alexandria. They have the power to do it and they cannot be stopped.
Best case scenario is Phyletism times ten (a problem which is plaguing modern Orthodoxy, is creating the Ukraine problem IOTL, and may prove to cause schism soon.) Worst case is Western fomented schisms. IMHO, it all depends upon whether
militarily the USSR takes Constantinople after WW1 and before the end of the Great Depression, or butterflies lead to the Greeks getting it. In short, Constantinople
cannot be in Turkish hands or schism is a foregone conclusion, because you better believe Turkey would be TTL's West Germany...propped up and militarized by the West a crap ton. A Constantinople inside the first instead of second world will be an opposing force in Orthodoxy. We could very well see all of the historical Patriarchates excommunicate the entire Orthodox second world. So, while the world would visibly look very Orthodox ITTL, in reality the vast preponderance would be schismatics! That, or, we would be having very interesting ecclesiological discussions (if the first world Orthodox churches excommunicated the second world, being they "Started it," would they be in schism? Then, what happens to the whole order of Patriarchates since Chalcedon with every single Church in schism? What happens to Canon Law? Is there a Council of Moscow that reconsistutes global Orthodoxy and officially amends ecclesial boundaries and primacy?)
If the second world has a toe-hold in the Middle East and controls the Constantinopolitan Patriarchate, then likely Moscow runs the show and the other churches simply go along with everything.
To end this rambling post, what is the end game? There isn't one. In a modern world, fascism will prove to be Russia's natural form of government. Orthodoxy works very well with it. I see no end in sight.
The economy of the USSR will be very interesting. Weapons, oil, grain exporting, much better medicine than ITTL. Knock-on effects on electronics and automobiles is possible.