Could be, but boxers do motivate themselves when they are in front of their opponents and vent everything like shouting or hurling trash talk and bad mouthing them in front of so many people.
Not sure why you mean by upstart, he has been a champion for years now, he is no beginner that suddenly become famous and champion.
He has earn it, this is his second reign as boxing's HW champion.
He is a strong boxer, but a very slippery person, he can refuse a rematch, citing mental problems, or announce his retirement, but after a while he will box again. I don't know, maybe it's my personal dislike against him, because I don't like people who don't keep their word. And I understand when, under adrenaline in the ring, a boxer can say anything, as Joshua did, but what Fury allows himself to talk about is too much.