[choppaface]

Not an answer, but Splunk currently has a large deployment of a C++ application that supports a large variety of platforms. At least as of a few years ago, they deployed C++ indexing and querying nodes on customer machines. They've spent a great deal of time to accommodate the peculiarities of enterprise customers, old compilers, etc. One might imagine that a "build once run anywhere" platform would benefit them, but they've found a business model where they were able to work around the peculiarities and still be profitable.

So while there's probably some interesting historical reasons that explain why there's no "JVM for C++", Splunk is a good example of a modern technical / business model where conquering platform fragmentation was feasible.