How did the Romans finally change their government after 200 years of harsh monarchic rule?

The Roman monarchy was not harsh. All the Roman kings, expert for the last one, who was a tyrant, were benign rulers. This king, Tarquinius Superbus, was deposed in a rebellion. The Romans decided to abolish the monarchy to prevent the return of tyranny. This was the purpose of the Roman Republic. The king was replaced by two annually elected consuls. Having two men in charge meant that they could counterbalance each other, The short term of office meant that no one could concentrate power in their hands.