The Romans did not want to take over Carthage and rule it as conquerors, they wanted it burned to the ground and all the citizens slaughtered. You don't do that unless you have powerful emotions guiding you.

They wanted Carthage's territory and wealth. They wanted to destroy a rival. Cato's famous expression (roughly) -- "Carthago delenda est!" / "Carthage must be destroyed" was his call to war. Rome had already fought two wars with Carthage, and Cato believed Carthage was becoming too wealthy and might again challenge Rome. Carthage must be destroyed.

Fighting against a rival to gain dominance is one of the most fundamental animal and human behaviors.