True, but at that time it was already too late. C/C++ had won.

Moreover, for a very long time GNAT had been quite difficult to build, configure and coexist with other gcc-based compilers, far more difficult than building and configuring the tool chain for any other programming language. (i.e. you could fail to get a working environment, without any easy way to discover what went wrong, which never happened with any other programming language supported by gcc)

I have no idea which was the reason for this, because whichever was the reason it had nothing to do with any intrinsic property of the language.

I do not remember when it has finally become easy to use Ada with gcc, but this might have happened only a decade ago, or even more recently.