What event caused the patricians to change the Roman government?

The patricians changing the form of government refers to the overthrow of the monarchy and the establishment of the republic. The Romans overthrew the last king, Taquinius Superbus, in a rebellion because he was a tyrant. They decided to do away with the monarchy to prevent the return of tyranny. This was the function 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 ensured that no one could concentrate power in their hands.

That the king was overthrown by the patrician aristocracy is an assumption, rather than a proven fact. Not enough is known about the events for this to be an established fact. For example, the leader of the revolt and the mastermind of the creation of the republic, Lucius Junius Brutus, was a plebeian. Moreover, 21% of the consuls in the first 26years of the Republic were plebeians.