I think that's part of the answer. Python has multiple independent communities of use: web, data science, ML, devops. Most languages only have one or two ecosys

I think that's part of the answer. Python has multiple independent communities of use: web, data science, ML, devops. Most languages only have one or two ecosystems of use. I think the other part of Python's success compared to JS is a better story about C integration. Python itself is just a series of macros to make C nicer to use, which meant the existing C/C++ ecosystem was relatively easy to integrate. And then the sci-py world also brought in Fortran. JS is huge on the backend web, but it hasn't spread into other ecosystems nearly as much because the C integration story isn't as good.