Brutus' speech in Act 3, scene 2, of William Shakespeare's Julius Caesar holds the attention of the people of Rome so well because they are all curious to know what their fate is. Given Brutus and his "men" have just murdered Julius Caesar, the Romans are without a leader. They are looking to Brutus for answers.
The speech also allows Brutus to prove Julius Caesar's ambition was too great to make him a good ruler. Therefore, Brutus needs to convince the Romans that Julius Caesar was far too ambitious to be a good king. Furthermore, the speech proves to be captivating given the language, honesty, and passion exuded by Brutus. Brutus wants to insure that the people of Roman understand why Julius Caesar had to be murdered. By the end of his speech, the Romans are completely on the side of Brutus. They all claim he has not offended any of them.