I don't think it would be accurate to say that the repetition of history is the main concern or most important theme in Shakespeare's Macbeth. Instead, other themes, such as psychological torment, the effects of guilt, the dangers of ambition, and the compelling gender dynamics inherent in Macbeth and Lady Macbeth's relationship take center stage. That said, there are elements of historical repetition within Macbeth. For instance, Macbeth, like the Thane of Cawdor before him, betrays King Duncan, and Macbeth is then betrayed in the same fashion by Macduff. As such, even if the central argument of the play is not necessarily that history repeats itself, we can see that much of Macbeth does focus on the cyclical nature of conquest and power struggles. This theme is represented by Banquo's ghost, whose presence suggests that the violent acts of the past (murder, in this case), never fully stay in the past and continuously leak into the present. As such, even if the repetition of history is not the central concern of the play, it is apparent that the cyclical representation of history is one of many important themes in Macbeth.