The correct answer is because he would kill his father and marry his mother. Even though Laius wanted to prevent this prophecy from happening, it eventually happened nevertheless - Oedipus killed Laius and married Jocasta, his mother, even though he did not know at the time who they were. That's where we have the Oedipus complex from.
Historians John Thornton and Linda Heywood of Boston University have estimated that of the Africans captured and then sold as slaves to the New World in the Atlantic slave trade, around 90% were enslaved by fellow Africans who sold them to European traders.