Shakespeare can be tough sledding for the average person. It doesn't scan like contemporary text; sound like contemporary speech. It's acted badly, mostly, by Americans I have seen. This same speech delivered by Charlton Heston is a hash. But he really wasn't much of an actor. Just popular.
But Brando can do it. The words, and the force behind them are instantly understood tripping out of his mouth. I think it's a kind of respect for the audience. He wants to make himself understood, both words and subtext.
Friends, Romans, countrymen, lend me your ears; I come to bury Caesar, not to praise him. The evil that men do lives after them; The good is oft interred with their bones; So let it be with Caesar. The noble Brutus Hath told you Caesar was ambitious: If it were so, it was a grievous fault, And grievously hath Caesar answer'd it. Here, under leave of Brutus and the rest - For Brutus is an honourable man; So are they all, all honourable men - Come I to speak in Caesar's funeral. He was my friend, faithful and just to me: But Brutus says he was ambitious; And Brutus is an honourable man. He hath brought many captives home to Rome Whose ransoms did the general coffers fill: Did this in Caesar seem ambitious? When that the poor have cried, Caesar hath wept: Ambition should be made of sterner stuff: Yet Brutus says he was ambitious; And Brutus is an honourable man. You all did see that on the Lupercal I thrice presented him a kingly crown, Which he did thrice refuse: was this ambition? Yet Brutus says he was ambitious; And, sure, he is an honourable man. I speak not to disprove what Brutus spoke, But here I am to speak what I do know. You all did love him once, not without cause: What cause withholds you then, to mourn for him? O judgment! thou art fled to brutish beasts, And men have lost their reason. Bear with me; My heart is in the coffin there with Caesar, And I must pause till it come back to me.
They used to call it Grammar School. It's the only school Shakespeare ever attended. It's the only school the greatest writer who ever lived needed. I'm told they used to teach grammar there.