Why no autotools anymore?

On 2023-Jul-10, autotools are dropped by a [commit](https://github.com/google/brotli/commit/d1fadddc940a23de3fad34c02879d7cfa6f86460). It seems that the current developers suggest to use CMake.
It is hard to have working CMake on some ancient platforms (without sufficiently modern C++ compilers), although it seems that C sources of Brotli are still able to be compiled with such platforms.

I wish if autotools are restored, even if it is only c/ subdirectory. What was the critical reason to drop autotools?