Yes Paul is a Youtuber, but Fury is hardly any better himself. Paul has dedicated his life to training for the past year, whereas Fury is regularly pictured partying etc. Paul is also naturally bigger.
Fury may be the actual fighter but his only opponent with a decent record he arguably lost again.
I agree with you that he beats Paul, but it isn't a forgone conclusion. If he loses it's damaging to his and Molly Mae's brand, best to just stick with easy fights and make millions. He's a smart guy.