Bhagavad Gita, Chapter 10, Verse 2

Neither the hosts of Devas, nor the great Rishis, know My origin, for in every way I am the source of all the Devas and the great Rishis.

Even the celestial gods are described as unable to trace this source back to its beginning.

Being older than the very beings who might otherwise explain it is offered as real evidence, not a boast. What comes first can't be measured by what came after.