Yes, I had the same thing: a jump from 4-5K reads per month to 20,000. It was four or five articles that spiked. It's all declining now.

I've been writing on the internet for 30 years. This stuff happens. It might be Medium. it might be something else. Sometimes an article goes up like a rocket and then crashes. Sometimes it goes into low orbit and draws a small but steady audience for years.

If Medium gave us access to our full logs, we could find out why. But they don't. So we don't.