I have a headcannon that after fanging out with the Ghouls, Brooke Paige gets inspired to write a fanfiction about them (I think that she secretly wants to be a writer).
It starts out like this. She knows every single FairyTale story, but none of the Monster stories, and this frustrates her. So she researches and, upon finding out most of what's been written are myths by normies, she goes to the ghouls and asked them their families histories. After hearing about all the trouble their parents went through in the great fright flight and establishing the monster world, she thinks about all the things the ghouls and mansters have been through and wonders: what would it have been like if THEY went through it. If they grew up in hiding? If it was them who decided to come out of the shadows, build relationships with the normies, and found the monster world?
She is so enchanted by the idea, she goes to the ghouls and explains her idea for her story and asks their permission to write it. They think it's cool and let her, with a few touches they'd like her to add (Frankie's dad had just made her a little sister, and she felt she was so clawesome that she wanted her written in somewhere, Cleo was mad at Deuce and wanted him to look like a dork,...ect)
So, with Ghoulia's help, she writes the story. What she doesn't realize is that, because of who she is, it becomes a real reality/dimension! She freaks out, and tells her parents. They tell her it's the danger of getting too involved in a story, and that because it didn't exist before, it doesn't have a narrator. So because she created it, she must become the narrator, and take care of that dimension because it's her responsibility.
After a while, it takes on a life of it's own. She narrates the story, but otherwise stays out of it because she's trying to be careful and wants to see how it plays out.
That's why reboot is different. Different but good. It's a parallel timeline/dimension to Monster High created by Brooke Paige as if the Ghouls lived in/through be hidden, founding monster high, coming out of hiding, and starting the monster world. What do you think?