It’s not really people revolting because of poverty. That happened all the time under feudalism and didnt result in new govt forms.
A super simple explanation is that Christian philosophers in love with classical Rome and the Greek city states started exploring the ideas like democracy and stoicism that were put forward by the ancients. After instituting versions that conformed to their cultural biases, they have been litigated to the point that have modern states.
There were revolutions and all that, but those happened all the time. This time there were an intelligentsia that believed in a more equitable political system.
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