3. People will believe that The Fiend can beat The Demon
It is well-documented that Finn Balor has only lost one of his 14 matches as a member of the WWE family while wearing his signature paint. It came at Takeover: The End, where he failed to regain the NXT Championship from Samoa Joe. It was his final Takeover before making his way to the main roster and he has upped his Demon record to 13-1 overall from the summer of 2016 to the summer of 2019.
In NXT, the Demon paint wasn't a different character. It was Finn Balor wearing war paint. He won all but one of his painted-up matches because he was booked as a dominant performer and a dominant champion (he held the NXT Title just shy of 300 days). On the main roster, Finn Balor and The Demon are two different characters, which can put WWE in a tough spot. The fans could ask, "Why wouldn't Finn bring out The Demon for his biggest match ever, against Brock Lesnar, one of the most dominant performers of all time?" There is no logic for Finn to decide not to become The Demon and fans cannot understand why he would need it for Baron Corbin, but not Brock Lesnar.
Corey Graves deleted his Tweet! More details HERE.
When The Demon comes out to play, it's assumed that he's going to win. That's been proven 6 times in 3 years. The paint goes on, Finn transforms into The Demon, and The Demon wins the match. However, in 2017, WWE decided to try The Demon vs. Sister Abigail, and many WWE fans thought it was going to be the end of the dominance of The Demon character. And that wasn't necessarily a good thing, because the vocal majority of people did not like the idea of Bray wrestling as Sister Abigail.
But again, people still believed that The Demon could lose to a transformed, more dangerous version of Bray Wyatt. The Fiend is an extraordinary character, and is clearly far more dangerous and brutal than Sister Abigail. If anybody can slay The Demon, it's The Fiend, and people believe it.