This is an extremely nuanced topic with thousands of mitigating factors affecting it in the real world and subjective definitions about what “power” means. “Doomed to fail?” What sort of a loaded question is this? Isn’t every civilization “doomed” to fail given the ultimately finite nature of life? If a democracy does falls to an autocratic uprising or autocratic, was it “doomed” to be so?

This question is just way way way way way too broad and to expect any sort of narrow or succinct answer. I don’t believe we can really say any form of government is more “powerful” than others or that any are “doomed” to fail (or we can be reductive and say they all are).