Producers are typically famous when they create something that creates a subset of their own genre or a major idea. Various volcaloid music vids are more memorable for the volcaloid used instead of who created the work because there are not memorable/important enough to be looked up. Don't get me wrong, a total fan or someone who pays more respect to the producer will look the producer up, but generally it doesn't happen with many people. Take the Evilous Chronicles for example. I instantly know that was created by Akuno-P/Mothy because I consider it a series of very major works and am a big fan of those works. However, I don't really know who created Senbonzakura. Even if it's stupid for me not to know, I just don't care as much.