Julius Caesar was power-hungry, and he was on his way to achieving his goal of having complete power over Rome and the empire at the time the conspirators struck. Marc Antony was not power-hungry before Caesar's assassination. He had the reputation of being a libertine. Cassius calls him "a masquer and a reveler." But Antony became power-hungry after Caesar's death. He helped Octavius to attain power and then shared the rulership of Rome with him and Lepidus. Lepidus was not an important character. He is disposed of in Shakespeare's "Antony and Cleopatra." Brutus was not power-hungry. He was a patriot and a philosopher. Cassius seemed to become power-hungry after Caesar's death left a power vacuum, but before that he seemed more concerned about protecting what he already had, including his personal freedom. Afterward he became avaricious. Octavius became exceedingly power-hungry and impetuous after Caesar's assassination.
How I see it is this way;
All the liberators/conspirators, excluding Brutus, were jealous of Caesar's power. Maybe not jealous, but they didn't want to be ruled by him, or any 'king'. Almost all senators, even the ones who didn't know about the conspiracy, didn't want to be ruled under one man, let alone, arrogant Caesar.
Don't get me wrong, Caesar is nothing of a tyrant compared to the monster he created (Octavian.) I'm talking historically, not in the play. So is Antony, all the cared about was revenge, money and control over Rome. Octavian then turned against Antony, who was ruling over their east part (including egypt) with his beloved Cleopatra.
Before that, Antony and Octavian started killing Senators, why?
2- To make people fear them.
3- Simply because they don't like them.
They also killed commoners so they won't have to give them Caesar's money will. They were greedy heartless monsters, weren't they?