
Tai F. answered 07/29/22
Art historian, linguist, museum professional, and editor
The short answer is that, despite everything the witches said and Lady Macbeth encouraged, Macbeth did not have to murder Duncan or commit any of the other acts that led to his downward spiral. Not only that, but his actions were done for selfish reasons and personal gain--namely, becoming king.
To quote Brooklyn 99: "Cool motive! Still murder!"