Final answer:
Shah Waliullah believed that the main problems of Muslims stemmed from a deviation from original Islamic teachings and moral decline, leading to internal strife and political weakness.
Step-by-step explanation:
Shah Waliullah believed that the main causes of the problems of the Muslims were a deviation from the original teachings of Islam and moral decline. This perspective points to the internal challenges within the Islamic world, such as infighting among different Islamic sects and the failure to adhere strictly to Islamic principles, which he saw as leading to political fragmentation and weakening society. The devolution of Abbasid power, conflict among Islamic rulers, and foreign invasions by Crusaders and Mongols were all symptomatic of this underlying cause. Waliullah's emphasis was not on a lack of military strength, Western cultural influences, economic resources, or trade imbalances as the primary issues, but rather on the need for a revival and reformation based on authentic Islamic teachings and values.