This is part of a CNN news article I need to translate. I am not quite sure about what situation the phrase describes. Here is the part the expression comes from: "When did the light switch go off for you to say, oh, my goodness, things have really drastically changed and I'm in trouble if I don't change with them?"
You are reading a transcript of an interview, not an article, and as such the English may not be as polished as a written and edited article. Cristina Alesci (the interviewer) is referring to a light bulb moment, in which an idea or realization is formed, represented in cartoons by a light bulb over the person's head being switched on.