I assume it did not affect everyone indeed. However, a lot of "Top Rated" sellers, who were raking in good amounts of money saw their income fall drastically, while still providing the same quality of work. The only thing that changed was their Success Score being lower.

It's very hard to improve a metric when you don't know what are the criteria affecting the metric. I've reached out to Fiverr regaring this and they never bothered to tell anyone what impacted your Success Score. "Just do better", they told me.