I’d go further and say the seeds of the Roman Republic’s downfall was set during the second Punic war when so much wealth and territory was amassed and it mostly went to the top, follow up when the Gracchi brothers did their failed bid to change things, or the several genocides the republic did, such as the 3rd Punic war or what Julius Caesar did against the Gauls again concentration of wealth of power and eroding of any checks against generals seizing control.