y did crooks....

Crooks still wants very much to be part of the ranch, but he has clearly been rejected by George, as evidenced by George's giving Lennie and Candy heck for blabbing.

he changed his mind because she brought him back to reality. there was no such thing as equality and freedom. no for a black man (as he thought). He would never be free. so he decides to stay at a place where he can at least eat, drink and have a roof over his head.