Chinese foreign policy back then is something a lot of people have trouble with. For what it's worth, I think there's a realpolitik answer to why China did it - they knew the USA would intervene on the side of the compradors in any and all conflicts in China's region if the conflict was socialists vs compradors, and that meant the USA could establish a foreard deployment of activated military. If China intervened on behalf of the revolutionaries, the USA would redouble it's involvement and China couldn't defeat the USA. So the solution was to take the board position that the USA would normally inhabit, preventing the USA from entering the theater. By intervening on behalf of the compradors, the USA had no pretext for intervention and China ended up with a forward deployed activated military presence AND significant influence over the governments.

This interpretation is congruent with their approach to capitalism as well, taking up the position that the USA would normally inhabit in exploiting workers by freely allowing Western capitalists to get rich off of exploited Chinese citizens. This resulted in China occupying the space the USA would normally be in and also giving China significant control over the means of production while also making it impossible to spin a narrative that China needs to be destroyed for its behavior.

I think the problem is that in the mid 1900s, things actually weren't good for international socialism, it's just that it wasn't widely understood. The USSR was struggling to propagate it's own internal revolution. Remember, Lenin didn't want Stalin to take over but there was literally no one better for the job. Stalin, for all the good he did, went on a purging spree and STILL failed to secure the revolution against the counter revolutionaries. That means that by the mid 1900s the vanguard of the first successful revolution was already falling apart, and China not only saw it but called it out.

The USSR vanguard also made a ton of mistakes that hadn't been fully understood by the 1950s including religious persecution and economic bloc isolation. China's revolution was an incredible advance in not just Leninist vanguardism but in elucidating dialectical materialism itself. And China made huge mistakes that needed to be analyzed and corrected. And by that time we're talking the end of the mid 1900s.

Meanwhile the USA was for the first time seeing an ascendant Black Power movement and American Indian Movement, which they promptly crushed and co-opted.

Meanwhile Europe was busy doing Social Democracy to pull the wind from the sails of workers movements and the die hard communists were still confused about materialism, dialectics, and the like. European communist movements, including the Cuban revolution (as it was led by European colonists, albeit true revolutionaries and traitors to their European heritage), were arguing that all forms of queerness were liberal bourgeois perversions.

And in Africa, while the decolonization movement was energized, it was clearly wrong in its strategy and tactics because by the beginning of the end of the 1900s Europe had reasserted its neocolonial hold over the continent.

I guess what I'm saying is that maybe their was revolutionary zeal in mid 20th century but things were not actually good. And we're now in a situation where the revolutionary zeal is way more subdued, but the periphery is once again reasserting itself. This time, however, it seems like the European war machine is floundering in ways never before thought possible and its racking up loss after loss without much to show for it. And that, to me, feels more hopeful than anything else. Instead of the Soviet perspective of building a better system to compete with the imperialists, China has shown us that it's possible to participate exploit the contradictions in imperialism to create conditions that imperialism simply cannot resolve and, thus, cause it to self-destruct.