If upvotes alone were deciding everything, the front page would consist of the few hottest topics repeated over and over, plus the indignation and sensation du jour. https://hn.algolia.com/?dateRange=all&page=0&prefix=false&so...
The reason why unregulated hivemind behavior composes to a dumb and unstable outcome is not that the people contributing are dumb. It's that they're only using a small part of their attention. If everyone here would deeply reflect before upvoting, flagging, posting, etc., about whether that action making the site more interesting in the long run, we'd get different results. But people don't put that level of attention into what they're doing here, nor should they—it's a lot of work, and everyone has more important things to worry about. What that means, though, is that the hivemind is mostly acting reflexively rather than reflectively (https://hn.algolia.com/?dateRange=all&page=0&prefix=true&sor...), which is bad for a site like this.
The solution is to have a small number of users (i.e. the mods) specialize in worrying about that, i.e. putting full attention into the site as a whole, and reflecting on it and regulating it (or helping it self-regulate) at that level. Then you get complex feedback loops between the big system (the community: large population, sporadic attention) and the little system (the moderators: tiny population, focused attention), which makes the site more unpredictable and interesting. Edit: software is also a critical part of this.