Indeed, I don't have a good understanding of the JVM ecosystem. However:
Google is tentatively on the hook for $9B for... essentially implementing its own JVM... or something. Doesn't matter to me, end result is that the future of Java on Android is far from clear. They're allegedly looking into using Swift as the next generation Android language.
RoboVM, one of the better / more popular ways to write iOS apps in Java was close-sourced, then acquired by Xamarin, then Microsoft, then shut down.
Oracle charges licensing fees for using JVM in embedded devices and kiosks.
To summarize, there's an incredible amount of tools and libraries for Java, but I don't like where Java's mobile story is going in general.
As far as I know the number of viable JVM machines you could build a business on is maybe... 5 at most? They're all experimental and/or abandoned.
Meanwhile, node / JS / ASM.js / Emscripten and friends are only getting better, faster and more widespread outside of the web.