The author has run into the same problem that anyone who wants to do analysis on the NPM registry runs into, there's just no good first party API for this stuff anymore.
It seems this was their first time going down this rabbit hole, so for them and anyone else, I'd urge you to use the deps.dev Google BigQuery dataset [0] for this kind of analysis. It does indeed include NPM and would have made the author's work trivial.
Here's a gist with the query and the results https://gist.github.com/jonchurch/9f9283e77b4937c8879448582b...