Final answer:
Plutarch states that Caesar's assassination stirred the Roman people to action due to their belief that he had been a champion of democracy and freedom, a sentiment further kindled by Marc Antony's moving eulogy.
Step-by-step explanation:
According to Plutarch, the assassination of Caesar inflamed public sentiment as the news exacerbated their sorrow and indignation. The Roman citizens felt a sense of injustice because they believed that Caesar had been removed due to his democratic leanings which threatened the authoritarian regime. The loss of a leader aspiring to restore a sense of freedom and shared rights deeply moved the populace. After Caesar's death, Marc Antony's speech further stirred the people to avenge Caesar's assassination, as depicted poignantly in Shakespeare's play based on Plutarch's work.