The play calling was strange, the line didn't hold up and Book didn't handle the pressure well.
I think, for whatever reason, the offense just couldn't get into any kind of rhythm and it effected the play calling. The offensive line has overachieved all year after losing Bars and I think we finally saw what most people expected would be an issue earlier in the year. And, Book isn't used to that kind of pressure.
I think it's pretty simple.