I took rapsey's item #3 to mean that languages tend to grow well when they're required—or at the very least considered the first-class option—for accessing a de

I took rapsey's item #3 to mean that languages tend to grow well when they're required—or at the very least considered the first-class option—for accessing a desirable ecosystem or platform, which does seem to be one major way language adoption grows. Not just that they let developers do things they maybe weren't before (but could have been, in another language).