Other mistake: When Jenny Lind is on stage singing 'Never Enough' during her American debut, she is in a very large theater with a crowded audience, and full orchestra. Obviously she would have to be miced, and have her voice amplified, for such a large space. When she is actually singing, her character's voice (or rather the dubbed voice of Loren Allred) is greatly amplified, with sound effects. But during this actual scene, there is no microphone or amplification system present. She does not have a microphone stand in front of her. There is no microphone hanging from the ceiling, or anywhere on stage that we can see. Technology was limited at that time, so she would not be using any type of cordless headset, or wireless microphone, which cannot be seen anyway. Her character's voice is obviously amplified a great deal through a microphone, which doesn't seem to exist.
Other mistake: When Charity makes her wish the spinning cage has almost stopped. However the lights continue to spin at speed around the family. (00:15:20)
Other mistake: Ann rolls down the rope and lands in Phillip's arms just as the camera changes. In the second camera shot, the rope that Ann has just rolled down is perfectly still. Not possible after Ann rolled down the rope less than half a second before. (01:03:00)
Other mistake: At the start, we see PT Barnum in the shadows. However his waistcoat is lit up in one shot despite the lights all being behind him. (00:00:40)
Answer: I'm pretty sure because she was a person of colour.