The conspiracy against Julius Caesar was a failure. The conspirators did succeed in killing Caesar but they were not able to kill the desire for revenge from the Triumverate. Because Brutus did not heed Cassius' warning about killing Antony and allowing him to speak at the funeral, it left the conspirators wide open for Antony's revenge. Antony is able to manipulate the plebeians during Caesar's funeral and get them on his side. Antony bids the plebeians to circle around Caesar's dead body, appealing to the Roman people's emotions and sympathies."Kind souls, what, weep you when you but behold Our Caesar’s vesture wounded? Look you here, Here is himself, marred, as you see, with traitors." (Act 3, Scene 2, line 190-193) Antony is able to rouse the anger of the Roman people. Once the mob mentality settles in, there is no turning back. They too, desire revenge on the conspirators. Brutus, in turn, loses the respect of the people he thought he was protecting Caesar from.
Great question. It all depends on perspective. It was a success in that it killed Caesar, but it was a complete failure if the goal was the restoration of the Republic.
The conspirators were all rounded up and killed and the final nail in the coffin was put in when Octavian took up power. From this angle, the death of Caesar may be seen as the end of the Republic and the start of the Empire.
There are a few reasons for this. First, the death of Caesar did not leave the people wanting a Republic, but a power struggle. Second, in that power vacuum, what actually happened was civil conflict. This was too much for the people of Rome. Civil war after civil war wore down the people in so many different ways. What they wanted was peace, even if there would be a new form of government. Third, it is also possible to argue that the Rome had gotten too big for a Republican style government. What they needed was an Empire that had a central government.