Why does my cat dont try to kill my bunny when he can?

well, i have 3 cats; 2 are scared of my bunny couse you dont wanna know what he did to them wehn pmy bunny was young. but my new cat he just want to attac but he dont! my bunny bites and stamps to my cat and roar. my cat just jump to my bunny and he show his sharp nails and than he tries to slap my bunny, is he playing with my bunny? i dont have to defense my bunny, he will do it himself. i watch how funny it looks but WHY dont my cat TRY TO KILL HIM? i know i have weird pets. ;D