peacock vs Zeus/Deus

There is an ancient belief that human soul is a winged creature. The idea behind the bird/soul metaphor is elegant and simple: your soul naturally strives to ascend in all possible ways: grow taller, stronger, richer, smarter, ascend spiritually, etc., - just like a bird strives to fly. We see winged creature/people depictions since Mesopotamia so no wonder everybody in the region shared this metaphor. Cuneiform symbol for name/penis (mu):

𒈬

Here is an illustration from Falnama (Book of omens, mid 1550s, Safavid Persian Empire):

As you can see this is a slightly different interpretation of the famous Bible Eden/Adam/Eve story, with a peacock in it, and this is not Quran. The flames around character heads signify their divine status, it's an old fire worship symbol which is still there in mid 1550s. Peacock is called heat-bird in Russia, because of the flame like spots on a tail:

This is another fire worship symbol which makes story more impressive: being the most beautiful bird, with a large "inflamed" tail, it's a living proof of fire worship idea and supremacy. Peacock in Persian is tawus. Official etymology denies it, but most likely it came from the same tap/tab root as city of Tabriz (hot stream), Georgian tapa (frying pan) or yoga tapas (heat exercises). The firebird was forgotten in western version of Adam-the-non-pious tale since peacocks don't live west of Persia.

There is an Indo-Iranian religion called Yazidism, - they worship peacock with 𐘾 at its feet (they have Serpent too). In Persian mythology they also had a Phoenix-like firebird called Huma. Phoenicians worshiped firebird Phoenix and used in their alphabet same "celtic cross" 𐘾 as Yazidis for letter tet, first letter of tawus. The cross is a stylized image of head/wings/legs, just like in Persian foru'har:

Not all crosses are crucifictions. Cross is a pre-christian religious symbol of a stylized bird. The crucifiction, if it existed the way it's depicted in Christianity, was referencing the cross/bird symbolism, not the other way around. The circle around the cross was a stylized symbol of huge peacock tail. Don't confuse it with the ring in the center of foru'har, or the one in the hand of the man, or in the claws of Egyptian Ba (personality) bird or the one on Egyptian cross. Those rings are symbols of loyalty/protection (wedding ring, circle of trust, circumsized skin, etc.) and existed before the fire worship (Mesopotamia, Egypt).

Greeks have a special alphabet letter psi, first letter of Ψυχή (psyche/soul). Letter is used as a symbol in psychology and psychiatry because it looks like it's flapping wings. Peacock in Greek is the same taˈos, almost like theos (god). They considered peacocks somewhat magical: Ancient Greeks believed that the flesh of peafowl did not decay after death, and so it became a symbol of immortality. Early Christianity adopted this symbolism, and thus many early Christian paintings and mosaics show the peacock. We say firebird but we mean a bird born from fire. Something that is born from fire and can fly is actually a smoke and heat. Given the etymology of Persian name for a peacock and the Russian name for firebird I'd say firebird is an euphemism for heat.

Rational explanation for such a global obsession with bonfires is fever and inflammation - miraculous phenomenons for ancient people. Prolonged exposure to heat during fire worship rituals could cure it (e.g. Sweat Lodges), which was probably sold to them as a religious miracle all over the world - check out all those flame-like tiaras from Indonesia to Russia (nevermind the archbishop, he knows he doesn't belong in this picture):