#2. The 'Death' of the old Bray Wyatt
Everything Bray Wyatt has done since he's been back as The Fiend has been choc-full of Easter Eggs, alluding to his former cult-leader gimmick, but especially that first episode of Firefly Funhouse where new children's television presenter Wyatt decapitated a cardboard cut-out of his former character.
Other allusions to Wyatt's former self include a painting of Wyatt's burning barn where the grave of Sister Abigail was situated being hung up on the wall by Wyatt, The Fiend still using Sister Abigail and, of course, the Firefly Funhouse puppets all having allusions to aspects of Wyatt's personality and former characters.
What makes this Wyatt's gimmick change different, however, is that usually when a Superstar goes away and gets repackaged with a new gimmick they completely sever ties with their old gimmick (Brodus Clay and Funkasaurus, Isaac Yankem and Kane are two fairly egregious examples). The Fiend, however, has been presented as a natural evolution of Wyatt and sits firmly on top of the foundations set by everything we've seen Wyatt do in the past.
You won't get a more pointed example of this than Wyatt's entrance at SummerSlam, during which he holds a new lantern, this one made out of the severed head of his former cult-leader gimmick.
What's particularly interesting is that Firefly Funhouse seems to exist in some kind of pseudo-supernatural realm, possibly entirely within Wyatt's own mind. However, when he decapitates the cardboard cut-out in episode one of Firefly Funhouse, he then actually manifests a severed head of that character that he's turned into a lamp in reality.
As you can see there are so many layers to the new Fiend character, and so many allusions to the 'death' of Wyatt's old character that it has to have been a long-term plan.