An atypical casting blunder by George Stevens.
Susan Strasberg was the obvious choice to repeat her Broadway triumph as Anne Frank. I have little doubt that she would have transformed a merely good film into a great one.
I'm reminded of the story of Jack Warner offering the "My Fair Lady" role of Professor Henry Higgins to Cary Grant. Cary told Jack that if he didn't cast Rex Harrison as Professor Higgins he (Grant) wouldn't even watch the film. Too bad there wasn't anyone with similar wisdom to talk to George Stevens.