What does Shakespeare's Julius Caesar reveal about betrayal to create the theme or universal meaning?

Shakespeare's rendition of Julius Caesar is arguably one of the most celebrated depictions of betrayal and one that has become firmly rooted in Western conceptualizations of loyalty.
The play hinges on the act itself: Brutus, one of Caesar's friends, participates in the plan to assassinate Caesar. The group of conspirators gathers to make a false petition in order to get close to Caesar; when Caesar rejects the petition (as they anticipated), the group descends upon him and stabs him to death. Brutus is the last to stab Caesar, causing Caesar to speak the iconic line, "Et tu, Brute? Then fall, Caesar."
The realization that his friend is willing to kill him to advance his own agenda is so devastating that Caesar willingly surrenders to his death, seeing no more reason to live or to lead if he is this untrusted and unsupported by those closest to him. Caesar's faith in Brutus--as well as in the political landscape he thought he knew--is shattered. This is an especially disturbing act, as Caesar knows Brutus to be a man of logic who acts in the interest of public good. Clearly, for Caesar, this is a moment of profound self-crisis and questioning of his own identity, not to mention the identities of those who have orchestrated his murder. As Caesar dies, he is forced to privately ask himself if he was truly a threat to the integrity of Rome. 
This depiction of the universal shock which accompanies betrayal also provides insight into the fallout that happens after such an act. Once the murder is complete, Brutus takes the pulpit to speak to the citizens of Rome. He defends his actions, stating:

If there be any in this assembly, any dear friend of Caesar’s, to him I say that Brutus' love to Caesar was no less than his. If then that friend demand why Brutus rose against Caesar, this is my answer: not that I loved Caesar less, but that I loved Rome more.

Brutus is arguing that the murder was a means to an end and that the death of Caesar will serve the greater purpose of protecting Rome. It is a plea for reason and for logic--one which is immediately dismissed by the poetic and emotional argumentation of Mark Antony, who states:

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.

It is ironic that Antony suggests that the crowd has "lost" their logic, since Antony is not appealing to logic but to pathos in his speech. This, again, emphasizes the universal experience of betrayal as difficult to interpret on a singular plane. For Antony, the murder of Caesar is an emotional crime that has ended the life of a great man; for Brutus, it is difficult but necessary political maneuvering--a sacrifice which will save an empire. 
Ultimately, while betrayal is horrifying and unexpected, it is also a tremendous act of clarification; it unmasks the true intentions of those around us, and it forces us to look inward at our own role and responsibility in our fate. As Cassius assures Brutus, "The fault, dear Brutus, is not in our stars, but in ourselves.”