Institutional power crushes the individual
The ward operates by making patients doubt themselves, depend on staff approval, and police each other. Ratched doesn't need to be violent because the system does the work for her. Every rule, session, and privilege exists to keep the men small.
Rebellion as the only honest response
McMurphy's refusal to play along is framed as sanity, not madness. The men who conform most completely are the most damaged. The novel treats resistance as the only way to stay human inside a dehumanizing system.
Sanity and madness are social constructs
Most of the ward's voluntary patients could leave but stay because the outside world feels more threatening. The novel questions who gets to define normal and points out that the definition usually benefits whoever holds power.
Emasculation as a tool of control
Ratched and the ward system specifically target the men's sense of masculinity and self-worth. Shame about sexuality, weakness, and failure keeps the patients compliant. McMurphy's counter-moves, the gambling, the women, the fishing trip, are attempts to restore that sense of self.
Sacrifice and inheritance
McMurphy's destruction is not meaningless. Bromden absorbs what McMurphy stood for and acts on it. The novel suggests that rebellion can survive even when the rebel doesn't, as long as someone else picks up what was left behind.