2. One of the most popular wrestlers
There aren't that many wrestlers who are a hit with the fans the very first time they step into WWE. That's the kind of following Finn Balor has. Even now, with the insane levels of talent the WWE has, there aren't that many wrestlers who can rival the following that Balor has.
He's a legitimate babyface and he's played the character to the bone for a while. The crowd cheers him everytime he steps to the ring or at any point wherever he makes an appearance.
Balor becoming the champion would get the biggest pop possible in the current scenario because he has been played down massively by WWE, to such an extent that he's now considered to be an underdog instead of being one of the top guys.
An underdog getting the push for the championship, who doesn't like that? That would get the fans on their seat.