Yeah, maybe read it again. The researchers are attempting to offer possible explanations. They don’t have any empirical evidence that domestic propaganda is the root cause or even a significant contributor to their actual empirical data. Further, they explain evidence later in the article that runs counter to that potential explanation - over the 15 years, the poor got more satisfied with the government. This tracks much more closely to economic and social progress in the country than it does to propaganda efforts, which were far stronger and more comprehensive in the early days of the revolution, necessitated by the presence of war both internationally and domestically.
Maybe don’t just skim the article for sentences that sound like they might jive with your preconceived notions and instead develop some critical thinking skills.