In this case it wasn't so much that Dream chose his audience, but that his audience is primarily impressionable young kids. I looked through the Reddit threads

In this case it wasn't so much that Dream chose his audience, but that his audience is primarily impressionable young kids. I looked through the Reddit threads that got posted around the time this happened and there were clearly a lot of young people who either chose to believe Dream because they didn't understand the statistics well enough to know it was BS, or were trying to rationalize that Dream was innocent based on some weird logic.