The politics in Macbeth are Machiavellian.  In The Prince (1532), Machiavelli said that "the ends justify the means."  He advocated a very modern political philosophy:

"the employment of cunning and duplicity in statecraft or in general conduct"

Likewise, Macbeth is very modern, light years ahead of its time.  Traditionally, a thane like Macbeth is supposed to honor, protect, and defend the King to his death.  But, with an idea from the witches and a plan from Lady Macbeth, he sees an opportunity to become King, which would not have been possible without murder.  He and Lady Macbeth play the gracious hosts who have daggers in their minds ("look like the flower, but be the serpent under't"), which reflects the theme of "appearance versus reality."

So, Macbeth focuses only on King, not on the murder he commits to obtain the crown.  Shakespeare shows the flaws in this power-play: it leads to guilt, madness, and losing one's head.