What young boy doesn't grow up admiring his father? Um. Jody maybe? Although the kid certainly respects Carl's authority, you would be hard pressed to say that he admires him. Instead, Jody tends to seek out admiration in the other men in his life—namely, Billy Buck and his Grandfather. Jody wants to grow up to be just like them because they embody that old western spirit of manliness and exploration. And in The Red Pony, that spirit is long gone. No wonder Jody tries to cling to it.
Having never had an emotionally present Dad, Jody would have admired anyone who gave him the time of day. Billy Buck is around all the time so that makes him a perfect candidate for Jody's admiration. But the ranch hand never really does anything to deserve it.
Jody's admiration for Billy never changes, even when the red pony dies.