Stronghold Crusharder HD don't want open. Im using macOS BigSur

From the product page:
Mac notice: The game is 32-bit only and will not work on macOS 10.15 and up.

You can thank Apple for that.

InkPanther is right. I can see you bought the game a few years back, so looks like a refund isn't an option.

The only thing that you can do would be to upgrade to a PC with either Windows (guaranteed to work) or Linux (might work).

Stronghold HD & Stronghold Crusader HD work out of the box in Wine, just FYI.

Which includes Wine on Macs. Yes you can have 32-bit Windows games running on a 64-bit only MacOS. You don't need to mess with Windows or Linux.

Thanks - I thought they would, but didn't want to say "definitely" as I don't have Linux myself and didn't want to give the wrong advice.