They can reach waaayyyyy more people with their message. For example, I don't watch TV, but if I see an online article, video, or social media post about a politician that I'm interested in, I'll look at it. In fact, the majority of what I know about politics I know from the internet. I can easily choose from candidates by Googling their platforms and reading their ideas straight from their campaign websites. It just makes information readily available to the public.