Why did everything kingdoms start fighting and capturing slaves from other tribes

The intensification of the internal or domestic slave trade occurred to feed the external slave trade. As slavers at the coast demanded more slaves, the pressure intensified in the interior for more slaves. Domestic slavers worked to supply the increased demand.

There are not a lot of natives anymore and they are all resorting to resorts that are not the best places to live most of them are in trailer parks and are still fighting for there rights to claim pieces of lands because of the expansion and people taking over there land