I don't understand why, but I believe I've observed similar. Possible hypotheses include: DHT Sybil attack? Hash ring bloat? Bad peers distributing exclusively

I don't understand why, but I believe I've observed similar. Possible hypotheses include: DHT Sybil attack? Hash ring bloat? Bad peers distributing exclusively irrelevant content? Wonder if this is a common observation, and if so, what kind of research might elucidate the underlying change.