I think that Macbeth is mad because in act 3 scene 4 Macbeth says “The table’s full.” when there is one seat left but Banquos ghost is sitting init and only Macbeth can see Banquos ghost.

Also it’s like lady Macbeth and Macbeth have swapped personalities because lady Macbeth is starting to show guilt. Also Macbeth is being overwhelmed with power I know this because he has sent murderers to go and kill his best friend banquo.