Democracy leads to better government in general, which leads to reduced corruption. People in Islamic countries accurately think their countries are corrupt: https://www.transparency.org/en/cpi/2022

Correlation vs causation. Those Islamic countries are still facing occupation especially from post WWI mandates like Sykes Picot and Balfour, and we see first hand the interest of "democratic" countries to keep things that way to ensure their superiority by force. They are not letting things take their natural course.