Anne Applebaum's review of Robert Harvey's Comrades: the Rise and Fall of World Communism says,

To be successful, he contends, communist revolutions had to combine at least four critical ingredients. They had to offer a quasi-religious creed, powerful enough to replace indigenous religions. They had to take place in newly industrialised, newly mobile societies. They had to take place at a time of popular discontent. Finally, they had to be flexible enough to absorb old nationalist and feudalist authoritarian traditions into a synthesis that seemed both new and familiar to a given society.

Like fascism, Harvey argues, communism was a reaction to economic modernisation, and to the globalisation of capitalism that began in earnest at the beginning of the 20th century. Invariably, communism succeeded wherever there was a large population of recently displaced peasants, who had been yanked out of their traditional villages, and thrust into a bewildering and apparently valueless industrial world. Communist ideology thrived on the sense of disorientation that people experienced when deprived of older belief systems. At least for a time, it successfully explained the world to people who found it inexplicable.

Hmm, Islam seems to work the same way for many people.