It's always going to be difficult to make a book into a live play, just like it's also going to be difficult to make a book into a movie. I want to think the book hides a lot of thoughts, foreshadowing and many dramatic effects which will have to be dramatized in a physical form, so it's going to be hard to fit it in with 2 hours.
People will start getting bored when it takes too long, unlike a real movie. So I guess this is why it's rushed.