According to bartolomé de las casas, the factor that motivated the colonists treatment for the natives was that they were greedy for more goods, gold, silver, so on.
Bartolomé de las Casas was a 16th-century Spanish colonist who acted as a historian and social reformer before turning into a Dominican friar. He was one of the first Spanish (and European) settlers in the Americas. Moreover, he was the first resident Bishop of Chiapas, as well as the first officially appointed "Protector of the Indians".