Rome did have elections (ever heard of the Roman Senate) and economic trade (every heard the term, 'All roads lead back to Rome), those are two of the main reasons why it existed so long. You cannot fund a military, if you don't have money. And pillaging is not cost effective by itself.
Now, get back to me, when you actually know something about history.
Of course later - after Augustus - all of that became nothing but show. They continued to hold elections for consul, but all real power was held by an emperor for life. Who was initially simply a military dictator, and later became something more like an appointed line of kings each naming his successor. Punctuated by regular civil war over the "crown". German armies fought each other for this crown for some time, before one of them decided he'd rather be called king. Charlemagne tried to revive the title (in the west - in the east it never lapsed, until the Turks conquered Byzantium in 1453) several centuries later, and that attempt became the later basis of the holy roman emperor office in Germany.
The Republic died long before that. In reality as opposed to in name, it died well before Augustus, when Pompey and Julius Caesar had all the real power, and the senate was just a pawn in their rivalry. They each ran enourmous client parties based on extending "citizenship", rewarding veteran soldiers, distributing offices and spoils of war, etc.
From its founding, Rome lasted centuries as a small and local traditional monarchy, a few centuries as a republic during which it conquered most of the Mediterrean world, a hundred years of civil war and successive tyrannies during which it added modestly to those possessions, and many centuries again of monarchy once more, initially military but becoming more and more traditional over time, during which it was itself gradually divided into spoils.
From the initial Roman kingdom (over what amounts to a small town) to the fall of Constantinople was over 2000 years. It is hardly surprising that practically everything that can happen in human government happened at one time or another in that immense period. The entire history of the US is the blink of an eye by comparison.