Why did European colonists slaughter local aborigines when they arrived in America, and then went to Africa to sell black slaves for labor?

Because the aborigines have their own settlement structure, and are full of rebellious spirit, adhering to the tradition and refusing to cooperate with European invaders, Europeans can only exploit America by selling slaves in Africa.

As a result, Native Americans were almost extinct, and the invaders established a new country on this land, and their original cultural history was exhausted.