Well, I'm really talking about rank-and-filers, here. There weren't many Indians among the leadership of the Latin American left, simply because the structures of Latin American society tended to preclude it. Political leaders tended to be from urban backgrounds, which meant that even if they weren't necessarily from a privileged background, they were still likely to be Spanish-speaking whites and mestizos. Indigenous peoples, in contrast, were mostly from rural backgrounds, and consequently at the periphery of formal politics. There were of course exceptions, going all the way back to Benito Juarez and beyond, but by and large their participation was primarily grass-roots, so I don't think global geopolitics is an entirely satisfactory explanation for their attraction to revolutionary socialism. Both their indigenism and their socialism began very locally, with the stuff of day-to-day life, and worked up from there. As you say, many nationalist intellectuals identified Marxism as a vehicle for nationalist programmes, and there's a body of argument that, post-1945, that's really what Marxism-Leninism was in a global context, but they're really a very different set of people altogether than the peasants and poor labourers who make up the greater part of the indigenous population of Latin America.
(There's probably a comparison to be made between the archetypes of the radical priest and the Marxist intellectual as mediators between indigenous and bourgeois political society, educated individuals who "go to the people", imagining themselves as the bearers of a doctrine of salvation, spiritual or material, but who attract a following because peasants recognise them as a national or global vehicle for their own local grievances, interests and ideals. But, I'm probably not the person to be making it.)
