Thanks! I looked for those as you suggested, but there only thing resembling an executable file in the main Kerbal Space Program directory is the game saves. Right now, the directory that the game is located in is "/users/user/library/Application Support/ Steam/steamapps/common/Kerbal Space Program". The KSP.log, KSP.app, and KSPLauncher are in this directory and the app runs if I open it using that file directly instead of opening it through steam.
All the resources, plugins internals, etc. Are missing from that directory and it looks like equivalents are located within the GameData subdirectory. There's one KSPSteamCtrlr.dll within there, which I think is only a module that allows steam to control the app.
So maybe it's an operating system thing, like you said.