What is it about Lennie that makes him so disarming? (In chapter 4 )

I'm not sure how disarming Lennie is. People quickly realize that there is something wrong with him. Slim notices that he is like a kid. I suppose his sense of innocence attracts some people to him. Lennie, for example, doesn't understand the meaning of racism so he feels free to talk with Crooks like Crooks is a human being. He also talks to Curley's wife because he doesn't understand why other guys keep away from her.