Rome was only as successful as it was because it was built from the ground up based on two of the strongest pillars in existence; military tradition and divine tradition. Military tradition makes for tradition itself, unity, and respect for the people you fight beside, while divine tradition makes for judgment, purpose, and respect for tradition itself. This brings a fervor into the general populous, making for a larger quantity and a higher quality of soldiers. Beyond that, the idea of a professional military was preposterous to even the soldiers themselves despite being one of the most professional militaries in the world, all conquering and combat was to support Rome itself, not to line their pockets with money. Even further, the ancient patricians were very smart people, because they made up fictuous history to further cement the traditions and customs of the common Roman man, what better way to convince someone than to tell of what their ancestors did? The first ruler incorporates brute strength and victory, the second patience and absolute peace with religious teachings, the third combines them and displays that you need both religion and combat strength, the fourth establishes the patrician role in society, the fifth and sixth further cements important values and also encourages expansion, while the seventh was made to display why the patricians must be allowed to be in power at all times because kings are bad.
Unlike the common person who was fed all of this misinformation and thus believed in it, rich families were as they are today, power hungry and with no respect for the law nor man, you'd be hard pressed to do anything about that without someone even further up the chain of command, but on top of the patricians making this an impossibility, that also riddles the political landscape with plenty of new issues. Either you have a monarch family and risk consolidating power to an awful king with no acquired skills, or you have elected dictators where you risk corruption. Rome did something inbetween, where they had to elect dictators with proven former experience, likely they had to be liked by the public, they had very temporary time, and if they did ever step out of line they'd get killed by the very people serving them, as it would be the highest order of sacriliege they could ever witness.
Despite this, the common man did have something to his advantage. He could in very good faith turn on his superiors if that was perceived to be better for Rome, so while the patricians were in charge, they at least had to be careful that the plebs didn't get too agitated.
Rome had no culture of its own besides warring and various traditions that all lead to warring, that's why the vast majority of their culture is directly stolen from the Greek. But that worked out very finely for the Romans, expanding further and ever further. Another important facet of Roman ruling was to never interfere in local customs or religion, all they did was force tax payment by way of money and men, as well as influencing them into becoming more similar to the Romans over time. They'd also set harsh examples if their hand was forced by unruly subjects.
Skipping ahead quite a bit, my theory on the fall of Rome is that it began falling apart when the idea of fighting for cash became a given. Whereas in the past you fought for Rome, now you fought for money. Even worse is that more patricians turned up and forced the necessary plebeians out of their farms, meaning that the tradition of the farmer warrior became a thing of the past, now forcing them to seek work that earns them money instead of simply farming crops and fighting for Rome when they are needed. It is also likely that the people grew more and more careless of Rome itself when Rome became an invincible empire with no equal nor opposition. Every war started from that point onwards could not possibly be disguised as anything but needless greed for more power and more people under its rule, making the few who weren't already, aware of the state Rome has come into.
But that's simply my view on things.