Rome kept winning military victories for centuries. The Punic Wars. Hannibal. Scipio. Cannae. Every time, Rome adapted, learned, came back stronger. The institutional system kept functioning even under catastrophic battlefield defeat.
Then something broke. Not militarily. The system broke internally. The Third Century Crisis: 50 emperors in 50 years. The empire didn't lose a war — it lost the ability to make a decision about who gets to make decisions.
The empire didn't collapse because it got weak. It collapsed because it got tired. Expansion exhausted the decision-making infrastructure. At some point, adding more territory, more people, more conquered regions to assimilate means you can't hold the center together anymore. You can't even maintain an internal hierarchy anymore.
First wire (obvious): Empires overexpand and collapse due to resource exhaustion and inability to defend borders.
Second wire (deeper): Expansion creates distributed decision-making (locals need authority to govern locally), but distributed authority requires central legitimacy to stay coherent. Rome's genius was the Hydra model — become Roman, adopt law and religion, reproduce the system locally. But you can only reproduce a system as fast as you can communicate it, enforce it, transmit its logic. There's a tempo at which expansion breaks the culture's ability to propagate itself.
Third wire (uncomfortable): The same mechanism that created durability (institutional distribution, local Roman-ification, cultural propagation) is what made expansion literally impossible to sustain. You can't add territory faster than you can make it Roman. And the bigger the empire, the slower the propagation. Expansion reaches a mathematical ceiling, not a resource ceiling.
Cross-domain — Psychology:
Essay seed: "The Mathematics of Assimilation" — you can't have both rapid expansion AND cultural propagation. One of them has to slow down. Empires that maximize one (speed of conquest) sacrifice the other (depth of cultural integration) and don't last. Empires that maximize propagation (thorough assimilation) can't expand fast enough to become true continental powers. Rome found the middle and lasted 500 years, then hit the mathematical ceiling.
Collision candidate: Does this collide with the Alexander hub's claim that vision creates momentum? Yes — Rome proves you can have slow, steady momentum without charismatic vision. But does slow momentum avoid the succession problem? Also no. Rome's succession problem just comes later (Third Century) not immediately.