The Star Wars saga ends. The first three parts of the Star Wars saga had a more complicated tale to tell- namely how a Republic becomes a totalitarian state. Telling the tale of the collapse of the Republic is a more challenging tale to convey than the more simple story of good vs. evil that permeated chapter four through six.
In the Phantom Menace, the Republic was paralyzed with political intrigue and showing signs of fraying. In the beginning of the movie, the trade alliance attempted to take over the peaceful planet of Naboo. Naboo mixed a monarchy and democracy, a peaceful version of England, and the Republic itself was a loose alliance of various worlds, with the Jedi acting as the main enforcer of the peace. Jedi attempted to mediate the conflict between the trade alliance and Naboo, but their efforts failed to keep the peace. Behind the scenes, a powerful new force was working to overturn the Republic and destroy the Jedi order.
In history, Republics often are weakened from within before collapsing. After years of Civil war, Rome shifted from being a Republic to an Empire. Augustus accepted the crown of Emperor while maintaining the fiction of Republic. But the fiction would eventually fall by the wayside. The Roman Republic collapsed due to responsibility of Empire and increase corruption within the government. Money became the tool to bribe the electorate and various interest groups as domestic spending increased.
Empire does not automatically mean shifting to totalitarianism. The British Empire encompassed nearly a quarter of the world population for almost 300 years before breaking up. England decline after World War II was due to the socialistic policy enacted as well financial obligation due to winning World War II. Yet, England never fell prey to dictatorship despite being an Empire.
Adolf Hitler, one of history real life evil men, arose from the ashes of Germany parliamentary government established after the First World War. He got himself elected by taking advantage of the chaos caused by the Great Depression and the feeling of betrayal that many Germans felt after losing the First World War. He used democratic rules to overthrow the democracy that existed. And no one seems to complain, as many Germans were ready to allow democracy die just to end the chaos.
Many Romans felt similar thoughts when Augustus ended the Republic. When Augustus took power, he ended years of civil war and strife while restoring order. Order took precedence over freedom. The Star Wars Saga indicated that similar thoughts were going through many of the Senate when they conferred special power upon Supreme Chancellor Palpatine to form a special Army to deal with the separatist movement and later surrender their authority to the Chancellor. (Of course, Palpatine is also the evil one behind all of this.) Palpatine used the Senate laws to undermine the Republic as the Republic fought against a separatist movement. The Civil war ended the Republic.