In Shakespeare's Macbeth, Macbeth's tragic flaw is vaulting ambition. He says...
I have no spur
To prick the sides of my intent, but only
Vaulting ambition, which o'erleaps itself
And falls on the other— (I.vii.25-28)
Macbeth's "vaulting ambition" is responsible for his "social ambition." Macbeth is not interested in money. He is a decorated soldier for Duncan—King of Scotland. Before their battle with Norway, Macbeth is already the Thane (Earl) of Glamis. Because of his exceptional valor and achievements for crown and country, Duncan gives him another title, Thane of Cawdor (taken from Cawdor—a traitor) as well as all that comes with the title, such as money, land, etc.
It is more Macbeth's desire to have absolute power that drives him to kill Duncan. Sadly, like Brutus in Shakespeare's Julius Caesar, Macbeth loves Duncan—who is his King, as well as his friend and his cousin. Additionally, Macbeth (when Duncan is murdered) is the King's host—it was unconscionable to kill someone enjoying your hospitality: even if he were your archenemy! And above all, perhaps (which speaks to Macbeth's descent into immorality), is Macbeth's betrayal of Duncan, for Duncan greatly loves Macbeth!
Elizabethans would have been familiar with the concept of regicide— to kill a king was a mortal sin. This is because they also believed in the Great Chain of Being, which was a hierarchy of all things on earth—God was at the top, followed by angels (for example) and then kings, men, animals, plants, etc. God (they believed) ordained who would be king—so for a man to alter God's plan, he forfeited his immortal soul. Elizabethans would have struggled philosophically and morally as to whether it was ever justifiable to kill a king—even if he were a tyrant as Macbeth becomes.
Macbeth argues first with himself (and then with his wife) against killing Duncan. He knows that it is a sin against God. Here, Macbeth notes that the sin of killing Duncan would be so great, that even the heavens would cry out in distress—for Duncan is not only King, but he is a honorable and ethical man. Macbeth makes note of Duncan's good deeds—
Hath borne his faculties so meek, hath been
So clear in his great office...
...that Macbeth is certain they will literally cry out for themselves like angels, and the sorrow over his death will produce tears and grief louder than the sound of the wind.
that his virtues
Will plead like angels trumpet-tongued against
The deep damnation of his taking-off... (16-20)
Lady Macbeth is also socially ambitious. Like her husband, she wants the power that being queen will bring her. When she hears of the witches' prophecies—realized in Cawdor's title and promised in Macbeth's kingship, she begins planning Duncan's death immediately—hoping Macbeth will come quickly so she can whisper poisonous things in his ear, strengthening his resolve to commit murder, which some goodness still within him might shy away from:
Hie thee hither,
That I may pour my spirits in thine ear,
And chastise with the valor of my tongue
All that impedes thee from the golden round,
Which fate and metaphysical aid doth seem
To have thee crown'd withal. (I.v.23-27)
The heroic figures in the story, Banquo and Macduff, have no social ambition—only loyalty to King and country, unlike Macbeth.