Wouldn't Russians only move to Dzungaria or Manchuria if these areas were actually annexed by Russia?
Manchuria was under Russian control before Russian-Japanese War after which it fell under Japanese control. One would assume that had Russia won that war or if it is averted Manchuria would be heavily colonized as was planned by Russian government ( and partially implemented IOTL; Harbin for instance was majorly Russian until 1930s).
With Dzungaria maybe I didn’t get
@Gloss ‘s idea but IMHO there is no much reason to build railroads into Dzungaria if Russia doesn’t at least has de-facto control over it like it had of Manchuria.
How do you make Russia stronger economically during this time?
Now that is a very difficult question that I don’t really know how to answer. There are of course specific small decisions that could locally somewhat increase Russian economic capacity, but the general solution is probably earlier and/or more radical abolition of serfdom. While I think the latter was definitely possible it is a very major PoD that would dramatically.
Fortunately a decision to create Orenburg-Tashkent railroad in 1870-1880s does not necessarily require such massive changes in Russian history. It was on the table IOTL and could have been made without other major butterflies.
So, had the language policy of a surviving Tsarist Russia been pro-Russian and anti-Kazakh, the Russian advantage in Kazakhstan would have been even more significant, correct?
I definitely think so. As I wrote earlier ( sorry for quoting myself but I don’t really want to rephrase it):
If we butterfly away Soviet language policy that greatly supported local languages ( at least in most Soviet Republics other than RSFSR) and/or intensify Russian colonization of the region Russians can probably assume at least three quarters of modern Kazakhstan population.
Arguably incredibly fertile Fergana valley can also be made plurality Russian. There was a pretty substantial Russian settlement of the area IOTL and given how divided local population is ( there are local Uzbeks, Tadjics, Meskhetian Turks and Kyrgiz constanly feuding with each other both in XIX century and today) if local administration implements divide and conquer policy among locals and if Russian settlement has strong governmental support Fergana can probably have Russian plurality ( of course including assimilated local people how chose to identify themselves as Russians to avoid constant internal struggle )
Additionally of those people who would continue identify themselves as Kazakhs many could have Russian as their mother tongue ( as many OTL Tatars who don’t now more than several hundred Tatar words).
In fact for Kazakhstan having Russian-language majority we don’t really need any sorts of early butterflies. Keep Soviet Union and Russian would be most spoken language in Kazakhstan ( even if many speakers would identify themselves as Kazakh).
Outside of OTL Kazakhstan two places most likely to have substantial Russian population outside cities are Chuy Valley ( that had Russian majority IOTL) and Fergana valley ( that can at best have Russian plurality).
What about significantly expanding the size and population of these cities as a result of migration, though?
Oil and gas industry doesn't need that many people though. And there is really no much other reasons for Russian person to settle in OTL-Turkmenistan than said industry. So at best I can see these towns remaining largly Russian-speaking thus keeping stable 15-20% of Russian population.
Also, how inclined do you think that Central Asians would be in regards to marrying ethnic Russians (or Ukrainians, or Belarusians)?
They would as they did IOTL. Intermarrige is one of the main tools of assimilation after all.
BTW, in last posts we are not talking about Christianization of locals but more about Russian colonization and assimilation. The latter is much more feasible but does this variation actually fit into your desired premise?