Gotta admit, Rosa kinda called it.

From Luxemburg’s The Russian Revolution, Ch. 3: The Nationalities Question:

While Lenin and his comrades clearly expected that, as champions of national freedom even to the extent of “separation,” they would turn Finland, the Ukraine, Poland, Lithuania, the Baltic countries, the Caucasus, etc., into so many faithful allies of the Russian Revolution, we have instead witnessed the opposite spectacle. One after another, these “nations” used the freshly granted freedom to ally themselves with German imperialism against the Russian Revolution as its mortal enemy, and, under German protection, to carry the banner of counter-revolution into Russia itself. The little game with the Ukraine at Brest, which caused a decisive turn of affairs in those negotiations and brought about the entire inner and outer political situation at present prevailing for the Bolsheviks, is a perfect case in point. The conduct of Finland, Poland, Lithuania, the Baltic lands, the peoples of the Caucasus, shows most convincingly that we are not dealing here with an exceptional case, but with a typical phenomenon.

To be sure, in all these cases, it was really not the “people” who engaged in these reactionary policies, but only the bourgeois and petty-bourgeois classes, who – in sharpest opposition to their own proletarian masses – perverted the “national right of self-determination” into an instrument of their counter-revolutionary class politics. But – and here we come to the very heart of the question – it is in this that the utopian, petty-bourgeois character of this nationalistic slogan resides: that in the midst of the crude realities of class society and when class antagonisms are sharpened to the uttermost, it is simply converted into a means of bourgeois class rule. The Bolsheviks were to be taught to their own great hurt and that of the revolution, that under the rule of capitalism there is no self-determination of peoples, that in a class society each class of the nation strives to “determine itself” in a different fashion, and that, for the bourgeois classes, the standpoint of national freedom is fully subordinated to that of class rule. The Finnish bourgeoisie, like the Ukrainian bourgeoisie, were unanimous in preferring the violent rule of Germany to national freedom, if the latter should be bound up with Bolshevism.

The hope of transforming these actual class relationships somehow into their opposite and of getting a majority vote for union with the Russian Revolution by depending on the revolutionary masses – if it was seriously meant by Lenin and Trotsky – represented an incomprehensible degree of optimism. And if it was only meant as a tactical flourish in the duel with the German politics of force, then it represented dangerous playing with fire. Even without German military occupation, the famous “popular plebiscite,” supposing that it had come to that in the border states, would have yielded a result, in all probability, which would have given the Bolsheviks little cause for rejoicing; for we must take into consideration the psychology of the peasant masses and of great sections of the petty bourgeoisie, and the thousand ways in which the bourgeoisie could have influenced the vote. Indeed, it can be taken as an unbreakable rule in these matters of plebiscites on the national question that the ruling class will either know how to prevent them where it doesn’t suit their purpose, or where they somehow occur, will know how to influence their results by all sorts of means, big and little, the same means which make it impossible to introduce socialism by a popular vote.

On Ukraine:

Or take the Ukraine. At the beginning of the century, before the tomfoolery of “Ukrainian nationalism” with its silver rubles and its “Universals”[2] and Lenin’s hobby of an “independent Ukraine” had been invented, the Ukraine was the stronghold of the Russian revolutionary movement. From there, from Rostov, from Odessa, from the Donetz region, flowed out the first lava-streams of the revolution (as early as 1902-04) which kindled all South Russia into a sea of flame, thereby preparing the uprising of 1905. The same thing was repeated in the present revolution, in which the South Russian proletariat supplied the picked troops of the proletarian phalanx. Poland and the Baltic lands have been since 1905 the mightiest and most dependable hearths of revolution, and in them the socialist proletariat has played an outstanding role.

…

The best proof is the Ukraine, which was to play so frightful a role in the fate of the Russian Revolution. Ukrainian nationalism in Russia was something quite different from, let us say, Czechish, Polish or Finnish nationalism in that the former was a mere whim, a folly of a few dozen petty-bourgeois intellectuals without the slightest roots in the economic, political or psychological relationships of the country; it was without any historical tradition, since the Ukraine never formed a nation or government, was without any national culture, except for the reactionary-romantic poems of Shevschenko. It is exactly as if, one fine day, the people living in the Wasserkante[3] should want to found a new Low-German (Plattdeutsche) nation and government! And this ridiculous pose of a few university professors and students was inflated into a political force by Lenin and his comrades through their doctrinaire agitation concerning the “right of self-determination including etc.” To what was at first a mere farce they lent such importance that the farce became a matter of the most deadly seriousness – not as a serious national movement for which, afterward as before, there are no roots at all, but as a shingle and rallying flag of counter-revolution! At Brest, out of this addled egg crept the German bayonets.

(The entire chapter is quite short so it’s worth spending the 10 minutes reading it)

Not just nationalism but also our naivete to how states act, regardless of whether they are 'socialist' or not. So many of the USSR's decisions prioritized the immediate interests/survival of the state at the expense of revolutions abroad and eventually those betrayals left it without the external support to survive the West's onslaught.