> Apparently Maven has 61.9M indexed packages.

Where did you see that number? Maven central says it has about 18 million [1] packages. Maybe with all versions of those 18 million packages there are about 62 million artifacts?

While the Java ecosystem is vastly larger, in Java (with Maven, Gradle, Bazel, etc.) it is not common to use really small libraries. So you end up with vastly less transitive dependencies in your projects.

[1] https://mvnrepository.com/repos/central

That is correct.