In Part II of this novel we see a change in McMurphy's attitude which comes when he realises that Nurse Ratched is the one who has control over when he is released or not and what kind of treatment he receives. He suddenly turns into a model patient and all of the other patients are extremely disappointed with this. However, what happens to Cheswick helps McMurphy to see that he has become complicit with the Combine, the forces within society that keep those who are branded "mentally ill" within the asylum, and that he needs to fight for the patients and himself again. Even though Chesick tells McMurphy he understands his reasons for not challenging Nurse Ratched any more, it is clear that Bromden suggests his suicide is a direct response of the loss of hope caused by McMurphy's conformity:
He told McMurphy this while we were all being taken over to the swimming pool. But just as soon as we got to the pool he said he did wish something mighta been done, though, and dove into the water. And got his fingers stuck some way in the grate...
It is strongly suggested that Cheswick killed himself because of the loss of hope that was the result of McMurphy choosing to conform to Nurse Ratched's rules and regulations. McMurphy realises through this experience the responsibility he has towards all of the patients, and this gives him the courage to begin opposing Nurse Ratched again, symbolised through his breaking of the glass to her office.