It's a superior alternative to cmd.exe. bash has never been a serious contender for Windows. Before PS you always wrote .bat scripts for cmd.exe (or .vbs for cscript.exe if you were really depraved). Nobody except Linux-first FOSS authors would expect Windows users to have cygwin / msys / mingw32 installed.
PS gave us a saner choice, though we would still usually bundle it with a .bat wrapper, just to a) make it double-clickable and b) set `-ExecutionPolicy Unrestricted`.
If you're asking "is PS better than bash", then sure it's better in some ways and worse in others, but that question only makes sense on Linux where bash is actually an option.