I've been interviewing and showing my book for editorial work for quite some time. So far, I have yet to be offered a shoot. I have been told by many different sources that I have been viewed as the top candidate. I just don't understand what's wrong.
…
How do I properly ask for that feedback? I'm not sure how to properly phrase the email to ensure them so I don't want to be viewed as hostile.

Thanks for the interview, I understand somebody else got the shoot. I was wondering if you could give me another half hour of your time, to help me learn what I need to do.