In "Brave New World" in what way does John change at the end of the novel and why?

John cannot accept contentment over happiness.  In order to have happiness, there must be tragedies, and the Controller tells the Savage that the Brave New World is not the same as Othello's word; there is "stability" in this world.  The Controller tells John that he must choose between "happiness and what people used to call high art." He goes on to tell John also that

God isn't compatible with machinery and scientific medicine and universal happiness.  You must make your choice.

John makes his choice.  Disillusioned with what he has thought that the Brave New World would be, he chooses to be alone away from everything that is the antithesis of what he believes.

I don't want comfort.  I want God, I want poetry, I want real danger, I want freedom....

Later, the Savage tell Bernard that he has eaten civilization, his own wickedness and it has poisoned him.  He seeks to purge himself and live alone in communion with Nature, for he belongs to no society.  But John has become a source of amusement and people fly in to watch his self-flaggellation.  When a young woman whom the Savage recognizes and calls, "Strumpet" while slashing at her with the ropes. When the crowd goes from the desire for violence to "orgy-porgy," John is caught up; he wakes later from soma and acts of sensualitiy:"Oh, my God!" he exclaims.

Realizing that he has already been made a sacrificial victim of the New World, John commits suicide.  Unable to have an authentic existence, the Savage chooses the only avenue he can.