Well, in the West, proletarians are still beneficiaries of imperialist superprofits, making them support the actions of the bourgeoisie and become a 'bourgeois-proletariat' as was described by Lenin in Imperialism, the Highest Stage of Capitalism (which he had observed in England at the time). In the global south, it's likely a large combination of factors. The most dominant one being that imperialism shatters the ability to educate the population, and installing puppet governments while violently repressing or castrating any effective communist creates a cultural hegemony largely free of class consciousness. Add to this the massive swathes of fascism that leak out of the imperial core in the form of propaganda and false narratives and you end up with a largely impotent proletarian movement in much of the global south. The average worker doesn't know enough and is more worried about 'getting by', helping their local community, or not getting blown up or killed by USian orc firing squads than organizing to overthrow Capitalism. With imperialism being the primary contradiction in the lives of millions of global southerners, the ones exploiting them are not visibly their national bourgeoisie, but rather the overseas American and European bourgeoisie. Thus the question for many radical sects in the GS becomes one of national liberation from the USA rather than the liberation of their class from Capitalism. Just look at modern Iran and Russia, which are becoming ever more galvanized against the USA while still being a predominantly right-wing nation/economy.
Despite all of those things being absolutely crushing, communism still finds its way into many liberation movements across the globe, and there are still many successful communist parties in the global south (some better than others).