Many associate C++ uptake to Microsoft, however they completely miss the point that C++ is a platform language.
It was developed on the same building as UNIX (so to speak), as C pre-processor with no additional requirements on C's toolchain.
That made it quickly available across all UNIX platforms and respective toolchains.
Then it followed C as younger brother alternative in any C toolchain that mattered.
A few UNIX vendors, e.g. Sun, did offer Ada compilers, but it was naturally an additional software package to buy, and not everything was available, thus additional hurdles to write FFI bindings.
Not bundling a language with a platform is always an issue with system programming languages.
However, I can't see Ada thriving without fixing their licensing. But on the other hand I don't know how well the Ada vendors could survive without charging for their compilers/toolchains.