How did they arrive at things like the 33 heavens, and the gods presiding over each?

I am looking at [Heaven of the 33](https://www.rigpawiki.org/index.php?title=Heaven_of_the_Thirty-Three) , where it says: > second heaven of the desire realm, situated on the summit of Mount Meru and presided over by thirty-three gods of whom Indra is the chief. Looking it up on [Wikipedia](https://en.wikipedia.org/wiki/Tr%C4%81yastri%E1%B9%83%C5%9Ba) , we get a list of more gods. I have had spiritual experiences, and have thought a lot about the structure of the universe (from a scientific and spiritual perspective). But never have I gotten into so much detail as to say "out of heaven, there is a second heaven divided into 33 realms, where the gods of x realm regularly battle with the gods of y realm". That would be so much detail, like figuring out that the brain really is divided into X number of functions (visual processing, reason, auditory processing, language, etc.), which took decades of research (or, one could say, hundreds or even thousands of years of thinking). It would be even harder than that, you would either have to reason "well, if perfection exists, then different types of perfection would exist, namely at least 33 perfections, where the whole system of perfections is controlled by a force which has XYZ features, etc..". And delineate crazy amounts of detail. Not only would you have to mentally be able to delineate it, you probably first would have to also deeply experience it in a soul-resonating sort of way! You would have to experience the reality of these heavens, then mentally break it down, then convert it into speech. So how did they do this? How did they arrive at such detail (the 33 heavens in this specific case, or even generally speaking)?