I *am* opposed to spam

> What proof do you have it's a Sybil?

I don't have proof, I am conjecturing based on what I consider most plausible. In logic this is called "Inference to the best explanation."

> Couldn't it be bag holders highly motivated to start to run nodes?

That can partly explain it. But I would be very surprised if the spike was entirely due to *real* new node runners and 100% of them chose Knots over Core. A sybil attack seems more likely, especially when it's so easy to do.