On some levels, it is a bit difficult to engage an audience with someone who ends up representing moral depravity. Macbeth is certainly a character who embodies some of the most ethically decrepit behavior. However, Shakespeare is able to engage the audience in this process. Part of this lies in how Shakespeare depicts the psychology behind human cruelty. Macbeth is typically human in the way he ends up embracing his brutality. Macbeth is not a monster that simply pops up. It is something that happens over time. Macbeth starts out quite loyal and rather decent. However, through the circumstances and conditions around him, Macbeth embraces an awful path. It is Shakespeare's understanding of human nature that makes this so engaging. In watching Macbeth, the audience understands that they are seeing their own condition on the stage. In his depiction of Macbeth's characterization, Shakespeare demonstrates a keen insight into human nature and psychology. It is this insight that engages the audience.
Another way in which Shakespeare is able to engage the audience is to simply show the arc of his development. The audience is engaged with how Macbeth starts off as unwilling to or incapable of doing something terrible and then easily further embraces acts of depravity. At the same time, the audience becomes engaged with how Lady Macbeth, once the pillar of unethical behavior, weakens and becomes unstable herself. This duality enables the audience to see the full scope and sequence of human capacity and agency. It is in this way that the audience is engaged. At the end of the drama, there is little in way of happy restoration, but rather an acknowledgement of the terrible capacity intrinsic to human beings. Shakespeare ensures that the audience is engaged as they arrive at this understanding.