I think the answer is, at least in large part, right there in your post. There is pretty broad knowledge in the industry of how to build cross-platform C++ app

I think the answer is, at least in large part, right there in your post. There is pretty broad knowledge in the industry of how to build cross-platform C++ applications, practices that weren't mature when Java took off, and this includes targeting IOS. Python and Ruby are great for automation and web development. Is there a need for One Language to Rule Them All? The JVM is the best part of Java IMO and I'm not really clear on where that stands in this current battle, but I know there are JVM implementations out there other than HotSpot.