I think the JS/TS ecosystem has an incentive to create small libraries because of the use in browsers. If a library is big, people will complain about it being bloated & poorly factored and full of stuff they don't use.
Now that everyone makes the libraries small and targeted, that means all apps have to either reinvent everything, or pull in many small libraries, which in turn pull in many small libraries, etc
And JS/TS have ancient history of having a minimalist standard library.