Shakespeare wrote Macbeth in 1606 during the reign of James I, king of England and Ireland, and former king (James IV) of Scotland. In Act IV, Scene 1, Shakespeare directly references this king with Macbeth's observation of "two-fold balls and treble scepters" in the succession of future kings, descendants of Banquo, in the apparitions the Weird Sisters conjure. This symbolizes the two coronations (Scotland and England) and countries (Ireland, Scotland and England) of James' rule and the ostensible Stuart ancestor, Banquo.
While it is true that Shakespeare wished to please his patron, the king, (who was also known to be interested in the supernatural), the playwright intended to capture a broad audience. Macbeth was performed at Hampton Court in London for the king shortly after the foiled Gunpowder Plot, an attempted assassination by James I's detractors. The porter relates this topical event in Act II, Scene 3. Shakespeare exploited the construct of the great chain of being in the play to warn its audience of what happens if you plot against your king.
The Royal Shakespeare Company observes that:
"People from all classes went to the theatre. The general public would pay a penny to stand close to the stage and interact with the actors. The gentry would pay to sit in the galleries, bringing cushions to make themselves more comfortable."
Shakespeare's plays were the popular entertainment of the Elizabethan age: the public would flock to see them in the same way that people flock to the cinema these days. It is not the case that with 'Macbeth', Shakespeare had a particular target audience in mind; it is not the same as the twilight series and its vampire romance tergetting teenagers with an interest in the gothic.
However, it is known that the reigning monarch at the time, King James 1 had a deep interest in witches and a conviction that they were the cause of much evil. Thus with 'Macbeth', Shakespeare is making the politically smart move of writing a play which confirms the beliefs of the King himself.
Shakespeare's target audience for the play Macbeth was no doubt King James I,the reigning monarch of England when the play was composed ,and his courtiers,because the play has a suggestion that the monarch was a descendant of Banquo,to whom the witches had prophecied that his future generation will be kings.Shakespeare has also traken care to characterise Banquo as brave and honest,which no doubt pleased the king.