Why would primordial, the most basic collection of cells, be at the top and not the beginning of the chain?

Primordial gods are considered to be a step above the other gods, they just don't care enough to rule. Imagine Zeus the God of Thunder trying to fight the primordial manifestation of movement and change. The gods are rulers of the universe, Primordials are the very foundation of the universe itself and could destroy it with a thought.

Even the Christian God before, he was retconned to be the only one, was only given such a high respect because he brought order to a small dot of Chaos and formed the earth. It's like taking a fort in a war while being completely surrounded for miles and considering it "defeating the enemy."