Even ClojureScript (which has JavaScript as a compilation target) runs on a JVM-based compiler and requires some buy-in into the greater Java ecosystem. Plus it is built around the Google Closure ecosystem which makes it largely incompatible with large parts of the modern JS ecosystem built around node (though there are ways to tap into these from CLJS but not vice versa).
Java itself is a very conservative programming language. It is getting new language features as new releases come out but it's very much not on the "bleeding edge" as language trends go. Its main target audience are big enterprises that need a reliable platform with a large market of competent developers (with qualifications available in the form of various well-established certifications).
That doesn't mean you can't do anything "cool" in Java or that there can't be any startup that starts out on Java, but it means the acceptance of non-Java JVM languages is a non-issue. That these companies already use the JVM as a platform just makes other JVM-based languages slightly more palatable.
Even ClojureScript (which has JavaScript as a compilation target) runs on a JVM-based compiler and requires some buy-in into the greater Java ecosystem. Plus it is built around the Google Closure ecosystem which makes it largely incompatible with large parts of the modern JS ecosystem built around node (though there are ways to tap into these from CLJS but not vice versa).
Java itself is a very conservative programming language. It is getting new language features as new releases come out but it's very much not on the "bleeding edge" as language trends go. Its main target audience are big enterprises that need a reliable platform with a large market of competent developers (with qualifications available in the form of various well-established certifications).
That doesn't mean you can't do anything "cool" in Java or that there can't be any startup that starts out on Java, but it means the acceptance of non-Java JVM languages is a non-issue. That these companies already use the JVM as a platform just makes other JVM-based languages slightly more palatable.