As it's March 15,

Presuming the plotters intended to save the Republic form of government in Rome, I would say they were right to do so.

If you look only at the reign of Augustus, it might appear that the people were better off under an Emperor than under two Consuls and the Senate.

But when you look beyond, to Tiberius, who was mediocre, Caligula, who was a disaster, Claudius, who was mediocre, and Nero, who was another disaster, it starts to become clear that emperors aren't automatically better, and could often be much worse than Consuls.

The history of the Roman Empire contains several great emperors, many mediocre ones, and plenty of disastrous ones. And the assassinations and poisonings that took place as men strove to inherit the empire deprived Rome of many valuable public servants.

There really wasn't much point. The senate had become almost irrelevant by then, the republic was finished. The senators lacked the military might to prevent Octavian becoming emperor. They might just as well have allowed Julius to become emperor for all the difference his assassination made. Except that perhaps Octavian made a better emperor than Julius would have been.