Why didnt chillingworth rat out dimmesdale?

Chillingworth didn't expose Dimmesdale because he was consumed by his desire for revenge and manipulation. By keeping Dimmesdale's secret, Chillingworth could exert psychological control over him, deepening both his own torment and Dimmesdale's guilt. Additionally, Chillingworth's obsession with Dimmesdale allowed him to justify his actions as a means of punishing the man he held responsible for his own suffering. Ultimately, Chillingworth's motivations stemmed from a combination of personal vendetta and a twisted sense of justice.