There's a hypothesis that the social order of a society depends on the accessibility of the military tech. E.g. in Ancient Greece almost any free citizen could afford to buy the top weapon of the time (an iron or bronze sword) - hence it was very expensive for a dictator to hire a force that could deal with an armed crowd - and this is why they had a democracy. Or a free person in the 13 American colonies could affor…
You have an historical mistake that supports your argument here.
Bronze weapons were very expensive, due to needing tin which could not be mined locally and needed to be traded for from as far away, such as the balkans, Germany or even Britain [0]. Because of this it was only available for the rich, ie the rulers and their supporters. Bronze age Greece[1] was not democratic, and was based around kingdoms, ruled by those who had access to the bronze weapons.
The later more 'equal' (but by no means equal at all, simply more so than ruled by tyrants, they still had slaves and oppressed lower classes. It's just there was a more numerous upper/middle class) greek states were in the Iron Age. Iron was much easier and cheaper to make as it was available in large quantities locally. This lead to to the iron age weapons and armour being much more widely spread [2] and therefore they had less powerful dictators.
Not all Iron age Greek states were democracies, and those that were would not seem like fair democracies today. But partially because of the more easily accessible weapons, the power in these states was less centralised than it was when the weapons were predominantly bronze.
[0]: https://en.wikipedia.org/wiki/Tin_sources_and_trade_in_ancie.... [1]: https://en.wikipedia.org/wiki/Mycenaean_Greece [2]: https://en.wikipedia.org/wiki/Greek_Dark_Ages