No single god sits at the top of the Hindu pantheon, and that is a structure rather than an absence. Vaishnavas name Vishnu supreme, Shaivas name Shiva, Shaktas name the Goddess, and each reads the other two as forms of its own centre. The atlas records this as sectarian supremacy rather than as an unresolved dispute, because the traditions are not disagreeing about a fact so much as occupying different centres of the same field.
Beneath that, the organising idea is emanation. The Rig Veda already says that the one reality is spoken of by many names, and later theology builds the point out at length: a deity may be an aspect, a consort, a portion or an avatar of another, and the relations run in more than one direction at once. A reader arriving from Greek or Norse material, where the gods are a family with a genealogy, will find this arrangement hard to draw as a tree, because it is not one.
Time is the third structural fact. Power here is not inherited from father to son but dissolved and remade. The kalpa ends, the world is withdrawn, and the same offices are filled again in the next cycle. Creation is therefore repeated rather than performed once, which is part of why Brahma, who performs it, receives almost no cult while Vishnu and Shiva, who sustain and dissolve, receive nearly all of it.
Mortals do not climb into this pantheon. The traffic runs the other way. Vishnu descends as Rama and as Krishna, taking a body and a lifetime, and the descent is the point: the divine enters the human situation rather than a human being promoted out of it.