Final answer:
The invasion by Saadi forces from Morocco contributed to the fall of the Songhai Empire.
Step-by-step explanation:
The fall of the Songhai Empire can be attributed to multiple factors, but one of the most significant factors was the invasion by Saadi forces from Morocco in the 16th century. These Moroccan forces were seeking to gain control of the trans-Saharan caravan routes, and they sacked and pillaged cities like Djenné, Gao, and Timbuktu. The looting and destruction of these cities rendered the Songhai Empire powerless and shattered.