So based on your premise, our current civilization should be dominated by strong, virile members who are natural fighters and respectable leaders.

Sorry, but our current version is anything but. In fact, I would say our current civilization is the antithesis of your model. I believe all of the pathologies you allude to are in full function today.

So it is with all civilizations. Without solving the why that this occurs, suffice it to say that it is as constant as the heavens that every civilization of our world history failed for essentially the same reason, that being a complete perversion of the natural order of things social.

The theory of civilization is sound. It is the practicality of the thing that falls apart in application, every single time. It should work; maybe it even does for a time, but eventually it falls apart and regresses back to something barbaric.

BTW, I do not consider tribal structures as civilized. Barbarians were tribal long before civilizations came along. To get to civilization requires at least three fundamentals; infrastructure, centralized government, and structured commerce. A common language and a currency would be additional characteristics, but not necessarily fundamental.
In civilization, you don't need a strong leader, just a lot of willing followers.

Perhaps therein lies the cypher.