JohnRawls wrote: Most of the Roman expansion was done under the Republic and Rome collapsed with the empire.
In fact the establishment of the Empire ended the chaotic, corrupt period of the late republic and ushered in the Pax Romana, the height of Roman indeed classical civilization, eloquently praised in panygerics of the second century.
Long term the dictatorial system wasn't able to manage the empire properly which impacted its long term stability with civil wars
The Empire arose largely because the
republic couldn't properly manage the empire. The irresponsible voters and special interests refused to treat provincials properly, leading to the social war and revolt of Sertorius etc. Julius Caesar realized that times had changed; the small city state in which the republic arose had become a vast empire of diverse peoples whose interests had to be brought into harmony with those of the Romans. Yet the shortsighted voters didn't realize this. Ergo the republic was obsolete and had to go. It did go and for two centuries the result was generally quite good.
and then finally was split in two because of those management issues.
The split was due to threats on multiple fronts at once. It's noteworthy that one result of the third century crises was the replacement of the principate with the Dominate. In other words to survive, the Empire
had to become more authoritarian not less. Ultimate failure in the west btw was due to loss of citizen support; it didn't stem from authoritarianism. Plenty of authoritarian regimes survived longer including the eastern empire.
The only authoritarian state that does good or did good economically without relying on x resource (oil) is Singapore.
Well, China hasn't been doing so badly…Authoritarianism btw often strives for increased state power not material enrichment of the masses.