Bailey doesn't have any name recognition. I'm surprised they didn't go with someone bigger.
I agree that the two movies seems like a bad idea. Universal seems to be showing a lot of hubris, IMO, by treating this property as if it were a superhero or sci-fi blockbuster with mass appeal enough to sustain two movies. Wicked is popular by musical theater standards, but not on the same level as Tolkien, Marvel, or even Frank Herbert (Dune), and the cast so far isn't going to draw much buzz. If the first movie gets poor or even mediocre/mixed critical reviews (which, based on the campy source material, it very well might) and tepid audience response, they are out millions for the sequel that will likely flop.