Yes, that’s a big part of it. Unity-based games generally follow most if not all of the framework that Unity defines, and since Unity itself is very well understood mechanically, that makes it very easy to find the right places to inject mods directly in between the game itself and the Unity DLLs that the game calls to act as a middleman or even completely replace the functionality that one side or the other would otherwise be implementing, and with that you can either create a mod on your own, or create a reusable modding API/framework for other mods to connect to. It’s not quite as straightforward as modding a game that is intentionally designed to be moddable, but in general, it’s pretty trivial once the basic setup work has been done and it’s almost the same for almost any Unity-based game so it’s not hard work to repeat on new Unity-based games either.