It wasn't until fairly recently
By "recently" you mean Win95? MSVCRT.DLL has been there for at least that long.
I believe that it technically belongs to Visual C++, not the operating system, but it needs to ship with the OS because the user space binaries are compiled with MSVC.
It was there but mystery meat vs whatever version you might need for your binary.
I believe that it technically belongs to Visual C++, not the operating system, but it needs to ship with the OS because the user space binaries are compiled with MSVC.