The temples are thought to have been built to honor the deified ancestors of kings.
This is a kind of ancestor worship, interpreted in Hindu terms. Living kings, courtiers, and others in ancient days would come to these shrines to worship these ancestors and receive boons from them.
The royal ancestors were thus lodged close to the god of the mountain, who was identified with Shiva, and who had ultimate power over the land.
The deified royal ancestors could serve as intercessors (in the middle) between the mountain deities and the living people of the land.