What drives John to hang himself?

Lenina arrives at the light-house, fueling John's anger, as there are spectators everywhere. He beats her with the whip, and then gives into the frenzied orgy that follows. When he awakens, he hangs himself. Losinng his individuality and becoming a part of the mob drive John to suicide.

He lost control of himself and took soma, whipped Lenina and participated in the orgy. he lost in whatever he believed in.