1. Moroccan Invasion: The arrival of the Saadian dynasty from Morocco, led by Sultan Ahmad I al-Mansur, in 1591 is considered the most crucial factor. Possessing superior weapons, including firearms and cannons, the Moroccans exploited internal power struggles within the empire to defeat the Songhai forces at the Battle of Tondibi. This military defeat dealt a significant blow to the empire and marked the beginning of its decline.
2. Internal Conflicts and Leadership Struggles: Before the Moroccan invasion, the Songhai Empire already faced internal challenges, including power struggles between different factions and leaders. The assassination of Askia Daoud in 1582 led to a series of succession disputes and political instability, weakening the empire's central authority. These conflicts made it difficult for Songhai to effectively resist the Moroccan invasion and maintain control over its vast territories.
3. Economic Disruption: The loss of control over key trade routes, particularly those in the trans-Saharan region, disrupted the empire's economy and reduced its wealth significantly. Songhai's economy heavily relied on trade, primarily in gold and slaves. With the Moroccan invasion and the diversion of trade routes through Marrakech, the empire lost its main sources of revenue. This economic decline further weakened the Songhai Empire's ability to resist external threats and led to its eventual downfall.