Answer:
Shakespeare's Macbeth is kind of a tragedy, and as he typically does with his tragedies he tends to restore the perception of political order, so killing Macbeth kind of offsets his previous brutal actions; the dim cloudy day is a simile to describe the story more vividly and emphaticly, since the plot although simple, it has many layers to unfold throughout, and it leaves the audience with a bittersweet aftertaste, with the feeling of: "it doesn't end with a sunny day but at least is not a thunderstorm"; for continuity sake.
Step-by-step explanation: