The most accurate response is: After Caesar’s death, Augustus expanded the powers of Rome’s leader.
Caesar’s assassins, believing they were preserving the Roman Republic, ultimately saw their efforts backfire as Augustus (formerly known as Octavian) rose to power and established a more autocratic system that concentrated authority in the hands of one individual rather than restoring the republic as they had hoped. Their actions did not restore the republic, but rather paved the way for the imperial system that would dominate Rome thereafter.