Inca religion was administered. The state organised worship as it organised everything else, by census, quota and calendar, and the pantheon reflects that: a ranked order of deities with the sun at its head, a professional priesthood, and a system of shrines around Cusco laid out along lines radiating from the Coricancha, each with an assigned custodian and an assigned day.
Inti, the sun, is the state god and the ancestor of the ruling line, which makes the cult of the sun and the legitimacy of the dynasty a single institution. Above or beside him stands Viracocha, the creator, who made the world and the peoples in it and then departed westward across the sea. That withdrawal is the reason the creator is not the ruler here.
Expansion enlarged the pantheon rather than replacing it. Conquered peoples kept their huacas, and principal images were brought to Cusco, which honoured them and held them as security. Absorption was policy, and it was also leverage.
The Sapa Inca was the son of the sun. At death his body was preserved, retained his estates and his household, was consulted, carried in procession and fed. The dead ruler did not vacate his position, which makes the boundary between the royal ancestor and the god unusually thin even by the standards of the traditions the atlas records.