1. they were already brainwashed to some degree. In the sense that someone made them believe things that were objectively either not true or arbitrary ("our rabbit god against their duck god")
2. these societies did have no mass media. Reaching many people of the society was only possible through elaborate structures and later the printing press, hence the influence of the back then most elaborate brainwashing structure there was: the catholic church. And even they had a lot of work to make this count as many people could not read the books they were printing.
The bible is a perfect example for how those societies in fact were very unprepared for being brainwashed. The fact that mass media didn't exist just meant the whole thing was much more time- and labor-intensive than a similar thing would have been today. Although I argue today the challenge would be to get as broad of a movement — because people were more isolated back in the day and therefore more scared to deviate from the perceived norms.
Hence why today's brainwashing movements, cults etc. always strive to isolate their followers from the rest of society.
I agree.
Which traditional societies burnt scientists (plural) for suggesting earth revolves around the sun?
Giordano Bruno comes closest and is perhaps what peppertree has in mind. But have a look at his Wikipedia article https://en.wikipedia.org/wiki/Giordano_Bruno for some more nuance.
See also the Wikipedia article on Galileo.
Many people have been burnt alive, Bruno included, Galileo excluded.
Bruno was a singular immolation for multiple heresy's, the Cathari were immolated en masse along with non heretics (for God to sort out) .. but none for claiming the earth traveled about the sun, Bruno (IIRC) made waves for denying actual core beliefs.
( Wikipedia cites Bruno not accepting the Trinity, the divinity of Christ, the virginity of Mary, transubstantiation, et al as the main items on the docket .. more than enough for the church of the time )
Galileo wasn't burnt at the stake and many would hold that despite popular opinion his trial had less (almost nothing) to do with his support of heliocentrism nor even his "mocking" of an old friend and now Pope as "Simplicio" and was instead rooted in the worst kind of corporate infighting - he had savagely insulted people that ascended to power within the church who seized their chance for revenge when it came.
You can always find a hook to hang people upon if you look hard enough, the actual reasons for wanting them hung are often orthogonal to any claimed in performative public trials.
Many would argue that the "highly educated, clerical class" of those times represented a rigidly traditional society that punished any who deviated slightly from their norms.
moderately educated, owning class: these can afford (at least some privacy for) their deviations, but in order to administer the economies which support their lifestyle, have need of the
highly educated, clerical class: these (having been deputised some power) must conform, lest they be rusticated into the
poorly educated, working class: these again get to deviate (because who cares); they've never ever been, and they're never ever going to be, any danger to the owning class.
But of course this tripartite division only holds true in Oceania (and Eastasia, and Eurasia); it clearly wouldn't in any actual earthly polities, right?
Post-republican China: self-punishment as first resort
Current-day North Korea: traditional society
Burning of people only happened in some parts of the world for some time. Religion is much more widespread phenomenon.
So it's hard to argue that one is a need of the other?
I think "immunity for brainwashing" is the wrong term. Back in the simple days people got less exposed to, how ever you would like to call it. The first ever printed western book was the f'ing bible and people in the 2000s thought the internet would spark a new era of education, you know, printing press 2.0 and such.
Ok, enough OT.
I'm pretty sure Australia was way more illerate at that time - plenty of cave and rock art going on for some 70K years prior, sure, but no written language at all even by 1788.
How do we know this?
The very fact of its emergence (and reliance on written teachings) speaks to the very opposite.
Then again, traditional societies had little to do other than farming and breeding ad infinitum, so there was limited value to any propaganda.