WWE likely scripts a lot of the nonsense he says. I wish they wouldn't. Let him shine, he's a better promo guy than the world champion Rollins, that's not an insult.
Actually I don't think they do script a lot of his stuff. They probably approve it, but I think he himself said on a radio show, a lot of it is out of his own head, that's why sometimes it sounds the same. Plus you can't tell me that creative would do such a good job on his promo's and at the same time do such an atrocious job on his booking.