One factor is that node's philosophy is to have a very limited standard library and rely on community software for a ton of stuff.

That means that not only the average project has a ton of dependencies, but also any given dependency will in turn have a ton of dependencies as well. there’s multiplicative effects in play.

This is my take as well. I've never come accross a JS project where the built-in datastructures were exclusively used.

One package for lists, one for sorting, and down the rabbit hole you go.

This is the main reason. Pythons ecosystem also has silly trends and package churn, and plenty of untrained developers. It’s the lack of a proper standard library. As bad a language as it may be, Java shows how to get this right.