Many of my old >1K star GitHub projects were not that great, but I always made sure to create the cleanest, simplest possible READMEs, inspired by things like the Python requests library's docs (https://github.com/psf/requests). I think it helped a lot in their success.

I remember someone once created a GitHub issue requesting I turn the README into some verbose technical thing with full API docs and a bunch of people replied saying they greatly preferred the "pitch + high-level examples" style.