You are correct that the JVM is ubiquitous in server software but not nearly as much as you assume and there has been a shift away from it in recent years for reasons having nothing to do with Oracle etc. I've been designing high-performance server engines since the 1990s and have watched the architectures and tool chains evolve.
Five years ago most new server engine development was done on the JVM. Since then there has been a shift toward new development being done in C++ such that the vast majority of new server engines I know about are being developed in C++ (mostly C++11) across a diverse range of companies. The reasons are practical and reflect the evolution of hardware.
The short version is that on current hardware C++ is much more efficient, both in terms of throughput per core and can achieve integer factor improvements in absolute performance relative to the JVM. Most of the differences are boil down to two things. First, server performance tends to be bound by memory performance and the JVM is quite a bit worse than what is easily achievable in C++. Second, an optimal high-performance server engine design in C++ is difficult to express within the JVM so basic design of the engine kernel tends to be less efficient as well.
In large-scale systems, that starts to add up in terms of power and hardware consumption and companies are more sensitive to this than they used to be. C++ currently offers significantly better characteristics and using less hardware to do it.