What is the purpose of Dryden's Absalom and Achitophel?

Through allegorical allusions to the Bible episode of King
David and his illegitimate son, Absalom, Absalom and Achitophel is
a satire of Charles II's political enemies. Although Dryden uses biblical names, his
readers could easily recognize Charles II in David as well as Monmouth and Shaftesbury
in, respectively, Absalom and Achitophel. The poem, which shows the plots devised by
Absalom and Achitophel to overthrow King David, celebrates the loyalty to the King by
his allies and discredits its enemies. Appearing in 1681, the work was thus a staunch
defense of the English monarchy at a time when the institution was under heavy criticism
from Parliament for the King's Catholic symphaties. In the same year of publication of
Absalom and Achitophel, the monarch dissolved Parliament and ruled
alone until his death four years later.