What factors led to the Spanish and Portuguese acquisition of empire in the Americas?

The Spanish and the Portuguese created several colonies in the Americas. One of the important factors for Spanish and Portuguese colonization of the Americas is the voyage of Christopher Colombus, the bloodthirsty ‘discoverer’ of the Americas. Colombus sailed under Castile Crown, but on his voyage home he reached Lisbon, the capital of Portugal, and met with King John II and showed newly discovered lands. So it was the Spanish and the Portuguese got basically a headstart.