Why did Pizarro break his word and have Atahualpa killed?

Pizarro broke his Word and had Atahualpa killed primarily due to his desire for power and wealth. After capturing Atahualpa, Pizarro saw an opportunity to eliminate a rival and secure control over the Inca Empire. Despite initially promising to release him in exchange for a ransom, Pizarro perceived that keeping Atahualpa alive could threaten his authority and lead to further resistance. Ultimately, the decision was driven by a ruthless calculation to consolidate Spanish dominance in the region.