No one but themselves to blame?????
Why would anyone attempt to find out.
This film adaptation is sold to the masses as a musical, nothing more - nothing less.
If you classy people know its all sung then that's bully for you. There's no law saying you should do research before seeing a film, if someone hears an interview with Hugh Jackman on the radio discussing the new musical he's in then who is to blame if that person takes him at his word and goes to the cinema to see it.
If it wasn't all sung you would have to cut out half of the songs