There has been much scholarly debate on the causes and effects of Islamist mobilizations. As some authors involved in this debate have identified rising Islamist attitudes among Muslims as a main cause of Islamist mobilizations, our study advances detailed research of opinion survey data as the best methodology to verify or falsify this assertion. Discussing the case of Indonesia, we use original survey data sets to show that prior to the 2016 Islamist mobilization there, Islamist attitudes were in fact moderating. This means that hardening Islamist views in the Muslim population could not have caused the mobilization. Importantly, however, we can demonstrate that Islamist political attitudes increased after the mobilization, and they did so consistently around the themes propagated by its organizers. This supports theories of religio-political entrepreneurs being the main drivers of Islamist mobilizations. Grievances and religious beliefs, on the other hand, are necessary yet insufficient conditions for such actions. © marcus mietzner, burhanuddin muhtadi and rizka halida.