During the 20th century, real-world communism (as opposed to the academic theory) always leaned on ye olde Russian imperialism, which, reincarnated under a new red flag, lent it the necessary muscle. Of course it was awkward to admit that the Communist bloc is actually an extension of the Russo-Soviet empire, so a lot of ink was spilt to recast the Russians/Soviets as liberators, bringers of peace and progress.

As of today, Russia is no longer even superficially left-wing in its state ideology, but the old personal and political ties to the far left in the rest of the world are still there. That is one of the reasons why "tankies" support the invasion of Ukraine and even cloak their support in the same "peace movement" jargon recycled straight from the Cold War era. That is also why countries such as Cuba, Venezuela and Nicaragua are sympathetic to the Russian imperial project.

Another reason is shared anti-Americanism, of course. The US has a much worse record track in Latin America than in Europe, no wonder that systemic competitors try to exploit it.