Oh I love Steam. I wanted to keep the Windows version around so I could benchmark it later. I renamed the Baldurs Gate 3 folder to something else so Steam wouldn't remove it when I uninstalled the game from inside Steam. Then I uninstalled it.

I hit the install button for Baldurs Gate 3... and it immediately shows the game as fully installed with no downloading? Of course, when I launch it, it shows an error because the files don't exist. Steam has no reason to believe they should exist because I told Steam to uninstall the game. I don't see how me renaming the folder should have caused that issue either.