To be frank, I’ve come to the position that the primary contradiction in Soviet relations with any of its fraternal socialist states was not principally any ideological discrepancies but the anxieties of its fellow state at being a victim of “big brother chauvinism” where its own individual state interests were subordinated to the interests of the socialist bloc - as set and determined by Moscow. I would say this contradiction is a leading reason for why the CPSU was unable to resolve any ideological gulfs with the other socialist parties it came into conflict with.

This was seen first with Yugoslavia, where Tito and the CPY tried to push for some market-based reforms and, as a result, was kicked out of the Comintern by Stalin, who also attempted to depose Tito from the CPY. Tito sympathizers were ousted from Communist Parties across socialist Europe and Yugoslavia was left to fend for itself, forcing it to ask the West for aid. To be a “Titoist” thereafter became the Comintern equivalent of the McCarthyist “Reds.” Churchill also accounted in his memoirs how Stalin decided with him to split Europe down the middle, leaving the Communist Party of Italy and the Greek Partisans out to dry in the Western orbit, where both were ultimately dismembered. Victor Grossman’s memoirs of his time in the DDR also recounts how a large amount of people were openly relieved that Stalin was succeeded by Khrushchev because of the reparations that was deeply hampering the state’s recovery and exacerbating its brain drain to West Germany.

This is not to say that the CPSU did not do a great deal for the assistance of its fellow socialist states and there are justifiable explanations for all of this conduct but nonetheless, just because something is justifiable doesn’t mean it fails to incur a cost. That cost was the view that Soviet interests took precedence over any Soviet aspirations of establishing equal fraternal relationships with its fellow socialist states and parties. In material terms, the USSR had a towering disparity in all measures - military, land, economy - and when this was coupled with perceptions of the CPSU’s “first among equals” attitude in the Comintern, it led to deep resentment that had catastrophic consequences for the socialist world.

It could be said that the CPSU’s attempt at this “inter-state democratic centralism” can be seen charitably as a “well-intentioned” attempt to take the first step towards that internationalist dream of breaking down the divisions of the states that divide humanity, but this was an ideal ahead of its time and failed to consider the conditions of its fellow socialist states. Most (actually, every single one with the sole exception of the DDR) of the newly socialist states were countries with a long history of foreign subjugation and torturous struggles for their sovereignty and when they finally achieved this sovereignty after WWII and yet were immediately expected to subordinate themselves to the CPSU’s leadership, it led to bitter feelings all around, even when Soviet side was acting with entirely good intentions, which was not universally the case.

This pattern continued all the way to the end of the USSR, with one of the most notorious cases being Honecker’s writing on how Gorbachev completely went past him to sell out socialist Germany by negotiating with the US and the West Germans without him. In short, there was a view that the CPSU failed to treat any of its fraternal socialist parties as equals, which is the source of the CPC’s accusation of the Soviet “big brother chauvinism” during the height of the split.

First impressions are important in all relationships and Sino-Soviet relations began distinctively on a bad note. The Comintern under Soviet direction demanded that the CPC join into the ranks of the KMT, which ended disastrously when Chiang Kai-Shek brutally purged all communists from the KMT and murdered thousands of communists and perceived communists. The understandable distrust from the CPC after the 1927 massacres led to a cooling down of inter-party relations and this lack of engagement led to a further lack of understanding which led to distrust from the CPSU when the CPC took power in 1949. It took Chinese military intervention in the Korean War for Stalin to finally trust Mao and see the CPC as a genuinely Communist Party - but the negative associations from the botched first impressions would be hard to let go of, as the later split would show.

When Deng Xiaoping met with Gorbachev in 1989, this is how he summarized his perspective on the Sino-Soviet split:

For many years there has been a question of how to understand Marxism and socialism. From the first Moscow talks in 1957 [among delegations from the Soviet Union, China and Hungary] through the first half of the 1960s, bitter disputes went on between our two parties. I was one of the persons involved and played no small role in those disputes. Now, looking back on more than 20 years of practice, we can see that there was a lot of empty talk on both sides. […]

[…] In 1963 I led a delegation to Moscow. The negotiations broke down. I should say that starting from the mid-1960s, our relations deteriorated to the point where they were practically broken off. I don’t mean it was because of the ideological disputes; we no longer think that everything we said at that time was right. The basic problem was that the Chinese were not treated as equals and felt humiliated. However, we have never forgotten that in the period of our First Five-Year Plan the Soviet Union helped us lay an industrial foundation.

If I have talked about these questions at length, it is in order to put the past behind us. We want the Soviet comrades to understand our view of the past and to know what was on our minds then. Now that we have reviewed the history, we should forget about it. That is one thing that has already been achieved by our meeting. Now that I have said what I had to say, that’s the end of it. The past is past.

https://www.marxists.org/reference/archive/deng-xiaoping/1989/196.htm