act of insanity on Ophelia was a test drive because he knew that if he could persuade her about his insanity then anyone would believe him.
But when Ophelia chooses her loyalty to her father over Hamlet that antagonizes him and he questions and degrades her. This is where we start seeing Hamlet sanity degrading and his insanity starting to empower him. Hamlet then interacts with Gertrude, whom he’s enraged at because he believes that she betrayed him and his father and played a part in his father and her former husband’s death. In his fuming anger he stabs Polonius violently thinking that it was the King. This is when Hamlet has lost his sense of reality and his act of insanity doesn’t remain just an act anymore. Hamlet gravely harms both Ophelia and Gertrude with his words of insanity, which were all unnecessary because ultimately they were innocent but Hamlet doesn’t even appear to be ridden with guilt nor does the thought of apologizing even cross his mind, all because he believes that his act of insanity will help him get the revenge that he’s obligated to get for his deceased father. His actions of insanity result in Polonius being sent to his grave but
not before Hamlet’s insanity takes another toll and he hides the body and goes to taunt the king about it. In the beginning of his act, Hamlet understood the potential of his madness act; but as his madness started to empower his sanity it began to blur his sense of reality and the consequences of his actions. Though Hamlet's plan of acting insane aids him in achieving his short-term goals of confusing and taunting Claudius, in the process of achieving this goal Hamlet begins to lose himself to insanity.
Hamlet behavior continuously changes throughout the play. In the beginning, one assumes its due to the loss and grief he’s experiencing due to his father’s death but after a while they get out of hand contributing to his insanity. Hamlet claims to love Ophelia yet he treats her the worst. It’s understandable that he was trying to full persuade her but when he was doing so he began to lose grip on reality and his behavior toward her was erratic. He tells her that he never loved her and he questions her character. His mood changes abruptly throughout the play which only adds fuel to his fire of insanity. He begins to act irrationally and stops thinking about his plan logically. He jumps aboard a pirate ship without actually think about the consequences of his actions. All he cares about is getting revenge and he is driven by this desire. Through this process he forgets about logic and his rationality with every step that he takes. Not only does he “accidently” kills Polonius in his rage of getting revenge, he hurts his mother, Ophelia and is responsible for Rosencrantz and Guildenstern’s deaths as well. In the beginning of the play he was contemplating whether it was better for him to kill himself rather than kill someone else and here he is now killing people left and right as he goes. His insanity isn’t allowing for him to realize the extremity of his actions and decisions about killing people. His original plan was just to get revenge for his father’s death but instead of doing that directly he is foolishly convincing himself to plot and hatch a foolproof plan when in reality he’s going crazy. As the play progresses so does the irrationality of his decisions. He appears to be a character who’s very logical and thinks through everything before he takes a step but all the thinking and the overthinking results in him being stuck in his imaginary world resulting him being insane. A simple act which began with Hamlet pretending to be insane in order to get revenge on his Uncle/King for his father’s death backfired dramatically as it resulted in Hamlet losing his sanity and his mind getting twisted and losing its sense of reality due to the constant switching back and forth. Hamlet’s insanity results in him being indecisive hence taking a longer time in getting the revenge which he could have easily gotten so much sooner if only he wasn’t sitting there idly and plotting his plans. His own plans take a toll on him resulting him turning insane.