I do appreciate it as a daily user of MSYS2. However the bigger thing that enabled them is indeed Cygwin project since it unlocked the path to build things that are using strict Unix tooling. autoconf, Make, bash etc cannot run under a pure Windows environment. They are too dependent to the underlying system being a Unix. To use pacman, bash and make in MSYS2, you need msys-2.0.dll. Even they cite Cygwin's URL in the runtime package [1]. And they basically patch Cygwin to enable this [2]

Without Cygwin enabling the path, it wouldn't be possible to build GCC for Windows without completely changing its build system. It would be a DOA fork while Mingw and PE32+ support is a part of GCC nowadays.

The nice and genius part of MSYS2 is that it is there to primarily encourage you to develop native Windows software that has better cross-platform behavior rather than Cygwin alone. If Microsoft made a better, free of charge C compiler in early 2000s that is adhering to the standards better, we wouldn't probably need Mingw to build cross-platform apps. Now MSVC is still free of charge for only open source and individuals.

[1] "Cygwin POSIX emulation engine", https://packages.msys2.org/base/msys2-runtime [2] https://github.com/msys2/MSYS2-packages/tree/master/msys2-ru...