In a nutshell: A lot of cultures (especially a lot of Native Americans) have a(n often harvest) festival that involves burning an effigy that represents negative emotions, hardship, etc. And it is generally human shaped because that made it a lot easier to spin it as “This effigy represents The Other tribe across the river. They are the bad people and the cause of all your problems” as needed.
And like 40 something years ago, a bunch of white artists were cranky that the locals didn’t want their input on what kind of paint scheme or sculptures would really make that ancestral tradition POP. So they made their own version in a desert with blackjack and hookers.
Then twenty-ish years ago, a bunch of rich folk and the nouveau rich techbros realized that these artists with their excessive amounts of hallucinogenics and “free love” lifestyle really know how to party. So they took it over as a way to party for a week or two every year.
And the key is: Regardless of your socioeconomic backgrond, you can come together with the joys of getting high, oogling some hot chicks, and appropriating some culture. All while talking about how this makes you a better and more enlightened person.
And in all seriousness: if you ever get the chance, go to an ACTUAL effigy burning festival. A lot of, generally Southwest, cities still have them and still respect the origins and it makes for a truly fascinating and, honestly, kind of spiritual experience as you learn, eat amazing food, and take part in something that goes back thousands of years… even if a lot of the Others were the American people…