Final answer:
Don Quixote goes insane due to his deep obsession with chivalric romances, leading him to perceive the real world through a distorted lens of knighthood and romantic idealism, as exemplified by his mistaking windmills for giants.
Step-by-step explanation:
Don Quixote's descent into insanity is primarily attributed to his excessive reading of chivalric romances. Consumed by these fantastical tales, he decides to become a knight-errant in pursuit of adventure and a grand purpose. His delusions lead him to perceive everyday objects as mystical challenges, such as the infamous windmills he mistakes for giants.
Quixote embarks on this quest with his squire, Sancho Panza, whose pragmatic view of the world contrasts sharply with his master's idealism. This juxtaposition creates a dynamic relationship, where Sancho's earthiness complements Don Quixote's madness and lofty ideals. The stark difference between reality and Quixote's perception symbolizes the conflict between idealism and realism, a theme that continues to resonate within various facets of literature and life.