This article discusses the role of radical Islamist groups – the Islamic Defenders Front (FPI), Hizbut Tahrir Indonesia (HTI), and the Salafis - in spearheading the populist Islamist 212 Movement. It examines why they were such effective forces in leading the movement and why their role diminished over time, which contributed to the decline of the movement. Drawing on political process theory and the literature on populism, this article argues that the movement faltered because they could no longer play an instrumental role due to the unsupportive structure of political opportunities, disorganized social movement, less relevant framing, and greater social and political pressure to the social movement.