Performing well in search results isn't just about SEO. It's also about content strategy. Just to name a couple of scenarios: You can have the best tags, descriptions, titles, etc. but if only a small population is searching for those terms, then very little are going to see your stuff. If people do happen to click and your content isn't compelling enough for them, then they're going to bounce off your video without watching it fully, which then affects your rankings negatively.
