To answer that question, think about the meaning of the phrase “keep them in the dark”. What does that mean to you? To literally and physically keep someone in a dark, lightless place? Not usually.
Keeping someone in the dark usually means to keep someone from being educated, perhaps withholding information from someone on purpose? With that understanding, we now know that “light” is not just electromagnetic radiation visible to the human eye. It is much, much more. Light… is knowledge.