The compiler was much faster, the tooling better, and it was easier to find knowledgeable programmers (we were spending quite a bit of time sifting through thick Ada reference manuals). Whatever correctness benefits Ada provided at the language level were more than made up for by C++'s productivity boosts (at the time) that allowed writing and running more tests and fixing bugs more quickly, resulting in code that was no less correct and easier to maintain and evolve to boot.
This was my experience of Ada as well. Beautiful language, that somehow seemed to combine the best parts of Haskell and C. But so difficult to find documentation online. C++ has it's footguns, but it's hard not to learn them all just from the background noise alone. The tooling and stackoverflow-ability makes C++ feel as fast to develop as a scripting language in comparison to Ada.