I didn't know Stiverne had a bandwagon Perhaps people who wanted to see Wilder lose for the most part? I think many simply viewed Stiverne as a capable puncher with some skill and experience, and Wilder as the more or less total unknown he was. This was a guy who had never been over 4 rounds or taken a single punch as a pro, how are you supposed to predict a big step up for a guy like that. There were no dumb picks for this fight, and probably not a single person anywhere who called it close.
Maybe Stiverne didn't expect that Wilder could hurt him the way he did, he was rocked at the end of the 1st and 2nd rounds where he made the first attempts to really let his hands go. I don't remember thinking he caught Wilder with anything huge himself, but he landed here and there and it was reasonable to doubt that Wilder could take anything!
If you rate Arreola the way I do, Stiverne was only slightly more proven than Wilder going in to the fight anyways. He looked terrible against Ray Austin, if Wilder had just leaked a video of himself sparring or hitting a heavy bag for 12 rounds it might have completely changed the Vegas odds