keatyjoe- In a lot of cases, a "star" being cast often helps the show to run. For example, I don't think the cast members of A Little Night Music are complaining that CZJ took away a job from another actress; rather, they know that her being cast allowed them to have a pretty good job. And I'm sure many people in Chicago have held jobs because of that show's stunt-casting.
Like it or not, actors in theatre realize that productions will sometimes be cast with stars. They may have worked countless hours, but it isn't as if the movie actor or recording artist hasn't. And besides, the people cast are also actors, so how is their being cast taking a job away from another deserving actor?
I am a firm believer in serendipity- all the random pieces coming together in one wonderful moment, when suddenly you see what their purpose was all along.