Couldn't that be solved in literally the easiest way if he represented the map as a X/Y coordinate system and disabled the rain effects whenever the player steps in the boundaries of the school? I doubt its a problem that requires hours and hours of fixes to make possible.
I wouldn't call the IP useless. Yandere Simulator is very well one of the most popular games on Youtube at the moment. Not on the level of Minecraft, Fortnite, Undertale, or the other big players, but big enough that there are hundreds of videos from multi-million subscriber youtubers with each video having millions of views. Hell, his channel alone for the game has something like 2.5 million subscribers, which is no insignificant amount. This drama aside, the game already has massive recognition, and new waves of children on youtube will be likely to see it and become hooked. Whatever company he will be contracting with sees the monetary potential in this game and the popularity of it independent from the Alex drama.
I don't know if its a million dollar game, but it should generate a few hundred thousand dollars if it were to actually be finished with all of the features and an environment which doesn't completely suck.