Rome was a proud republic (res publica: rule by the people). Its insignia, SPQR, stood for "The Senate and the People of Rome." They would tell and retell the stories of how they revolted against the Etruscan Kings during Rome's founding.
But eventually, the republic was torn apart by civil wars, both before and after Julius Caesar. The final civil war pitted Octavian against Mark Antony (and Cleopatra). Octavian and his talented generals won and took power in Rome. He killed off his enemies and consolidated power, like a typical tyrant. He took his father's name, and the Senate bestowed the honorific "Augustus."
However, the common Roman of the era would have no idea that he now lived in an "Empire." In fact, the title "Imperator" was a military honor that many earlier Romans had been awarded. The Senate still existed. Certain historians point out that it was not until the reign of Diocletian centuries later that Rome really acknowledged the end of the Republic.
Augustus kept the peace, however, and so powerful Romans, including senators, appreciated his presence. Also, in his own words, he found Rome "a city of brick, and left her a city of marble." He funded fantastic architectural projects, many of which can be seen today. He sponsored poets, including Virgil. Much of Rome's influence on the subsequent 2000 years - on Christianity, philosophy, architecture, and government - were impacted by policies enacted during his rule.
But that is still not an adequate explanation of how a tenacious, rebellious people like the Romans succumbed to Imperial rule. Several historians point to a simple fact: Augustus lived a long time. The average Roman of the era barely made it to the age of 35. Most people, at the end of Caesar Augustus's rule, had no real memory of the habits of the republic.
The people expected another "imperator" when he died. That was 2000 years ago this month, the month named after him.