Daniel.
BK to NJ, but always a New York Knicka
What the fukk is the drive or motivation behind the Funhouse and Fiend?
Funhouse Bray started off as a reformed Bray, which can easily be attributed to his friend with Matt Hardy, being put in that lake of transformation or whatever, but also a safe space for a mental breakdown from Bray's previous connections - the Buzzard, Sister Abigail, Huskus, etc. The character has had a supernatural element for as long as he was on the main roster, so fine, all that's already established in the canon of his character.
Save for Foley and King (I don't recall what connection there was to them), everyone he's attacked he's had some prior history with. Seth, going back to the Wyatt/Shield days. Balor, Kane, Braun in the Wyatt family, Bryan betraying the Wyatt family, everyone was a relic from Bray's past and there is a constant "you know what you did" alluding to their past.
His character is a mentally fractured, demonic representation of the Bray from before. The character is conflict - Bray trying to be "good" and reformed and learn from his past mistakes and hiding away in the funhouse and the evil in Bray fighting to come to the forefront and always seemingly winning that fight.
In comparison to Ricochets finger in the booty I'm a competitor, Humberto White Ranger, Randy I just RKO people out of nowhere, Black pick a fight with me and a myriad of other people on the roster that have no character depth beyond wanting to fight or run from a fight, yes, Bray's character has significantly more depth and in turn is more interesting than generic fighter A vs. B. As a result, more people are going to be into it - either for the inherent fukkery that comes from a character like this, or because it's something that is simply different than the vast majority of the roster.