Because the right Inca had to be recognized as auqui (Prince) for real panacas Cusco to be Sapa Inca. To meet this essential requirement, Tupac Yupanqui, who was in the conquest of Quito, with the royal family moved to Cusco. It is said that Pachacutec around both still alive and went to meet them to meet his grandson. It seems that the boy made such a good impression on the old and so he asked the child to lead the Inca army load the fortress of Sacsayhuaman, a ritual act. It is said that the prince did so well the business that made him Pachacútec your favorite and it cemented his future eminence as Inca.
Tupac would have named as his successor Capac Huari, but finally decided by Huayna Capac would provoking the wrath of Chuqui Ocllo, mother of Capac Huari. This fact seems to have been the trigger that prompted Chuqui Ocllo to poison Tupac Yupanqui. Later it said that Tupac Inca had changed his mind only when he was dying and the lost reason.
Given this fact, Achachi Huaman, a general loyal to Tupac Yupanqui (and his brother) hid Huayna Capac and after many lawsuits and outcry Ocllo Mama (mother of Huayna Capac) Chuqui Ocllo condemned and his accomplices to the penalty of death. As the small Capac Huari, not made any damage due to their innocence. However, banished him to a secluded spot under the supervision of people's confidence Achachi Huaman.
Huayna Capac, already declared successor to Tupac Yupanqui had as regent to his uncle Apo Huallpaya until it reaches adulthood. Apo Huallpaya later proposed to the throne to his son Huayna Capac arguing that it was unfit for office, Huaman Achachi Huallpaya Apo also knew he intended to kill the young monarch. Apo Huallpaya and his son were sentenced to death for treason