Why were there continuous political instability in west Africa between 1500 and 1700?

The period from 1500 to 1700 was a turbulent and dark period for Africa.

The Islamized African countries went into decline not only because of the loss of power of the Arabs, but mainly because of the explorations promoted by the kings of Portugal, who were founding a network of strategically located ports. The Portuguese found civilizations that had developed their own political and cultural systems,

Between the sixteenth and seventeenth centuries, Europe discovered sub-Saharan Africa, initially under the control of the Portuguese, who on their way to India found a source of wealth that was soon coveted by many others.

As European interest in Africa grew, the difficulties of their governments increased and thus destabilized the policy maintained by their governments.

Also considered in the era of more movement of slaves to industrialized countries.