It wasn't that the chin had the balls to shoot costello,it's what Vito would have done to him if he refused, so in turn you can say chin feared what vito, becareful using the word fear when speaking about gangsters, it's more of a healthy respect that they have for one another, nobody wants a war

"McGurn likes you, so I make you. So you are now one of us, if you fuck up, we take it out on McGurn. He is your sponsor. Fuck up, it's his ass. You work in his crew, he is your capo."