They weren't kidnapped. 90% were purchased from black Africans in Africa and then brought here. The slave trade had been going on internally in Africa and into the middle east for centuries before the Europeans wanted cheap labor after finding the Americas. African nations profited immensely from the slave trade. The colonization of Africa did not occur until after the new world mostly abolished slavery.

This does not change the hand dealt to the people bought and brought to the New World however.