From what I’ve read of the review of the ‘Affirmative Action Empire: 1923-1939’ by Terry Martin:
Martin significantly advances our understanding of the early, formative years of Soviet nationality policy, providing a subtle and lucid reconstruction of its unique conceptual underpinnings and its stormy evolution. Contrary to earlier Bolshevik mantras, Lenin and his partner in nationality policy, Stalin, committed the {union} by 1923 to developing non Russian languages, elites, territorial units, and cultural forms-all at the expense of Russian nationhood and culture. Hence the Soviet Union became, in Martin’s odd phrase, the first multiethnic “affirmative-action empire.”
That’s good, but then there’s this next part
Then, in the period of the Great Terror (1933-38), the experiment ended. Russian nationality and culture were revived, and “bourgeois nationalism” replaced “great-Russian chauvinism” in opprobrium
Why did that happen in such a manner?
Sorry, maybe that was a little antagonistic. I think user bennieandthez answered your actual question pretty well, that to the extent these policies existed, they dried up during wartime. When the Nazis invade and have cells throughout eastern europe, narratives of ethnic harmony got flattened into a desperate struggle for the survival of all the Soviet people. I’m not sure what these practices looked like in the postwar period, but even after the victory, Soviet authorities likely focused on reconstruction of vital infrastructure over something seemingly superfluous like cultural centers and what not. There was likely less to go around in general. Stalin would go on to die in 1953, and his death caused paradigm shifts which may have caused these policies to fade from view.