They found (weak) evidence of change. In order to confirm constancy, they would have to find significant evidence of no change.
This is not accurate. In the paper, the authors state that they are not able to conclude, so they suggest that more precise measurements are needed. Moreover, it is not possible to prove that there is no change by experiment. One can only demonstrate the effect, or determine an upper limit for it.
Your belief that Eastern Europe developed democracy without external influence shows your total ignorance about recent European history. Eastern Europe has received massive funding from the EU to build infrastructure and ensure economic development. Equally important is the political and economic integration across Europe, and the military strength of the USA that brings stability and a sense of security. The democratization of Eastern Europe is the result of determination and massive investments, and this is by the way the norm. Think about how the US treated Germany and Japan after WW2.
Those examples are in stark contrast to the how Iran has been influenced from the outside. Both the USA and USSR opted to support both sides of the Iran-Iraq war
Meaning simply that a conflict in the middle east was in the interest of both super powers, playing divide and conquer. Or was that also because of some cultural phenomenom?
To state that culture is the ultimate force in political developments is simply naive. Not only naive, it is dangerous. People like you scare me.