​Why did people assume an Asian woman in BBC viral video was the nanny?

This is a BBC News interview with Professor Robert Kelly. Suddenly, his two small children burst into the room while he was live on air This has been viewed hundreds of millions of times. BUT ... commenters on social media and initial reports from news outlets assumed that Jung-a Kim, the Asian woman who ran in to usher the kids out, was the (soon to be fired) nanny – not his wife. ​Did people assume that the Asian woman in his home was the nanny because she seems to behave in a subservient way? She seems scared, flustered, her posture is low to the ground and she doesn’t make eye contact or speak. Or is it that she can’t possibly be the heroine because Asian women are routinely depicted as secondary figures in the media, if they are visible at all.