]
Wicked the musical works as a musical because no one cares about the plot....just want to remind you of one scene of the musical
For example, in ONE scene of Wicked's second act, we (A) establish that Boq is now employed by Nessa, (B) establish that Boq isn't happy with this situation, (C) see the inciting incident of Elphaba's arrival, (D) learn that Nessa and Elphaba's dad is dead, and Nessa is the new governor of Munchkinland, (E) learn that Nessa resents her sister for not helping her, (F) see Elphaba attempt to fix Nessa's legs, (G) have Boq return to the scene and declare that Nessa has been taking away Munchkins' rights, (H) have Nessa, in a fit of rage, use a spell on Boq, (H) have Boq die, (I) have Elphaba cast a spell to bring Boq back to life before fleeing, and then (J) realise the "twist" that Boq is now the Tin Man.
And that's all in ONE scene, lasting no more than a few minutes. There's absolutely no farfanooging way that such an interaction could feel even remotely natural if it played out on a screen (Hell, it barely even felt natural on stage). Splitting the musical into two will allow time for two, three or even four scenes to cover the same events.
That's not gonna work in a movie at all.