It sounds like you downloaded the free Linux build instead of the Windows build. I think the itch.io download interface might be a bit confusing but you only get download links to the Windows and macOS applications if you pay $2 (or more).
is it possible that you can find a way to not have a paywall against the windows version? my family is very low on money and i really just want to play some cool game to pass the time without having to pay. please find a way to fix this, its kind of lying about it being free if you have to pay just to get a windows version. thank you!
There's already a way to get it for free. The entire source code is available here: https://github.com/keiwando/evolution, so you can download it and download Unity (also for free) and build the windows version yourself.