I think what happened is that music channels are primarily for people that don't watch music videos necessarily, so the algorithm promotes them basically to people which are doing like me, have YT in a tab somewhere, while they do errands, play computer, work on pc, they don't necessarily view videos. which is slightly rigged towards musicians which upload videos with video and put great effort into video. also trendy / upbeat / and also matching video footage seems to perform better for user satisfaction, they seem to view more and on repeat. :) think of short viewers more like a mechanism for discovering your video also they seem to go in a different area than long form videos
