because he sucks his toes
Curley attacks Lennie out of anger and aggression, blaming him for the death of his wife. In retaliation, Lennie crushes Curley's hand, revealing his immense strength and inadvertently causing Curley significant harm.
Curley does not want the others to know he lost in a fight against Lennie, a mentally challenged person.
So that he can avoid the embarrassment that he was beaten by Lennie. Slim is the one who warns Curley that if he gets George and Lennie canned everybody will find out about his loss and he will be the laughing stock of the area.
Curley thinks that Lennie is making fun of him through his silence. Lennie is very large and Curley is short. Curley is defensive about his height and dislikes Lennie's silence.
Not telling the boss about what Lennie did to his hand. Instead he must say he trapped it in a machine.
Curley was in the bunk room beating up Lennie. Curley was looking for his wife and saw Lennie laughing. Curley thought Lennie was laughing at him when he really wasn't. Curley then started to beat up Lennie while George is screaming to Lennie to fight back. Lennie then grabs Curley's fist as he is about to punch him again, and Lennie crushes Curley's fist. The damage to Curley's fist was so bad he was taken to the hospital. Slim forces Curley to say his hand was crushed by a machine. There were hardly any bones left in Curley's hand, and Curley was crying.
At first Lennie doesn't fight back, but then George says get Curley to Lennie so Lennie grabs Curley's fist and breaks his hand and doesn't let go until George starts slapping him.
Curley wanted to fight George I think, so he picked on Lennie. He hit Lennie a couple times and then Lennie stopped a punch in mid-air and squeezed Curley fist and brokenit ending his boxing career. Then Lennie Lille Curleys wife and he runs away and George kills him. :)
Curley fought with Lennie because he thought he was superior than everyone else on the ranch since he was the boss's son and since at that time, Lennie was laughing, Curley thought that Lennie was laughing at him. Obviously, as I said before, Curley thought he was better than everyone and he thought that he shouldn't be laughed at by such a low person so he punched Lennie because of his own stupidity and snobbishness.
Curley attacks Lennie out of rage and insecurity. He is a small man who feels threatened by Lennie's size and strength, and he targets Lennie in order to assert his dominance over him and prove his own toughness to the other ranch workers. Curley's aggressive behavior reflects his own feelings of inadequacy and a desire to prove himself.
Curley beat up Lennie in "Of Mice and Men" out of anger and jealousy. Curley was upset over his wife's flirtatious behavior towards the ranch workers, including Lennie. Being a small man, Curley also took out his frustrations on Lennie to assert his dominance and power over him.
Lennie breaks Curley's left hand during their altercation on the ranch.