what caused each change in rome's government? what caused rome to change to a monarchy, republic and them a dictatorship?

According to legend, Rome was founded by the descendants of the survivors of the fallen city of Troy, and sons of Mars (Roman god of war, Greek version: Ares). If you don't know the story, the twins Romulus and Remus were raised by a she-wolf, and when they grew up, the built the city of Rome. The city's first citizens were criminals, convicts, exiled people, etc. from Etruscan cities. The Etruscans were one of the native inhabitants of Italy. Back to the story, Romulus later kills Remus, thus, Romulus becomes the first King of Rome. He and his citizens later kidnapped women from the Etruscans, causing a rivalry between the two states. Later, some of Rome's kings were already Etruscans. The Romans disliked the way their kings ruled - thus the seventh king was deemed to be the last. They revolted, and were successful, establishing the Roman Republic with a Senate, and two praetor-consuls as heads of state. For a long time, Rome will keep its government this way, until the rise of Julius Caesar. During its Republic days, Rome experienced an aggressive expansion of their territory, as they had a method of thinking that "the best defense is offense". They tried to conquer anyone or anything that they perceived to be a threat to the power Rome was enjoying.
Rome began to expand to the whole of Italy, the former Carthiginian Empire (North Africa, Spain), Greece, Egypt, and more territories. Julius Caesar was also a notable contributor to this expansion, as he led several victorious conquests. This had gotten too much into Julius' head. He became too influential and powerful - other politicians wanted to get rid of him. On the other hand, he was thirsty for more power, declaring himself as a life-long ruler - a dictator. The Senate has had enough of it, and began plotting the famous murder. After his death, his nephew Octavius, who will later be named Augustus sort of sought some revenge, and became the first Emperor. Rome would stay an empire for the rest of its days. After centuries of being an empire, Rome was already unsustainable. Several attacks from different sides of the empire crippled it. Internal conflict didn't help at all. After three to four centuries of being an empire, it has split into two: the West Empire, and the East Empire. The West Empire didn't last long, while the East survived for another 1,000 years. The East tried to reclaim what the West had lost, and became a bit successful at doing so. At this point, Christianity was already widespread. It became the Empire's official religion. Catholicism from Rome also began to emerge, however, the East Empire had some conflict with Rome, thus the establishment of the Eastern Orthodox Church. After standing for about two millenia, it is undeniable that remnants of Roman government and society could be found in the structure of modern-day governments and politics. It has laid a very crucial block in building the modern-day world to what it is now.