What is Crook's dream and why is it important? Why didn't it come true?
It is in the fourth section that Lennie goes into Crook's sleeping place and chats with him. Crook never openly expresses a dream in this section, but it is absolutely clear that what he desires, like Lennie and George, is companionship to stave off loneliness.
It is important to take note how loneliness is described in this section. Crooks says to Lennie:
A guy needs somebody - to be near him... A guy goes nuts if he ain't got nobody. Don't make no difference who the guy is, long's he's with you... I tell ya a guy gets too lonely an' he gets sick
Crooks then reminisces about his childhood where he had the constant companionship of his brothers, which prompts Lennie to disclose his and George's dream to Crooks. Although initially sceptical about the chances of success, Crooks clearly wants in on this dream, offering his services for free to George and Lennie for a place to stay.
Loneliness is one of the key themes of this novel, and all of the characters are its victims. Crooks, by position of his skin colour, is another victim to loneliness, who is desperately looking for companionship to survive. He does not achieve it due to the death of Lennie but also it is hinted because of his skin colour and the prevalence of racism in the time of the novel.