For pure fukkery purposes.
Bray needs another vessel, again. But not just any vessel, one for power purposes because that's what consumes Triple H. Bray needs to take his power away. Bray needs :
Throughout the build I'd ambiguously imply that Bray's idea of a vessel might just be Stephanie's womb. A brush of the hair, lullabies, etc. Creepy.
So the match at Wrestlemania happens - Bray wins, but Triple H continues fighting after the bell. Harper and Rowan reunite and they put HHH down cold. They abduct Stephanie McMahon and they disappear.
Weeks go by where they don't find any of them. They send Renee or somebody on a field report each week trying to piece together where Stephanie and the Wyatt Family have gone.
Then at In Your House : Dominion, our field reporter finally catches up to the Wyatt family, where Stephanie is being held. HHH arrives not too long after and fights off the Wyatt family rescuing Stephanie. Stephanie looks a mess. Tattered hair, out of it, speaking in tongues etc.
The following weeks on RAW we piece together her story from sit down interviews, she isn't pregnant, nothing like that happened, she appears to be fine and of sound mind. Bray Wyatt is fired, being sued etc.
. . . That's when we tease things out. Stomach pains, vomiting, then she starts making irrational decisions. Ultimately we find out she is possessed by Sister Abigail.
Stephanie McMahon is Sister Abigail and Bray Wyatt is back at her side. The Whole World In His Hands.