Shout out iron lung for being so first-time horror watcher friendly. 90% of the people I know irl that saw iron lung in theaters (myself included) had never seen a horror movie before. And this may be unintentional on marks part, but it had ways for you to experience the universe before watching the movie.
The soundtrack coming out before the movie was in theaters was really nice, because if you were scared of jumpscares, the music can help you prepare for that. (i am just generally insane about soundtracks, but I did listen to the iron lung ost to prepare for watching the movie)
If you wanted an idea of what would happen in the movie? here's marks several playthroughs of the games and what he thought of it even before he was going to make a movie.
That part where he "sees" the eel for the first time and "talks" to it of "we'll stay in oposite sides and not mess with each other"(idk I only saw it once don't expect a direct quote) felt very much like markiplier playing a video game of how he tends to interact with the monsters and threats. and of all the things throughout the movie that part even almost made me laugh. After that part I wasn't really scared anymore bc I knew that I was mainly in for a performance that was going to be very good, and that while yes it was going to be scary, it was mark, and that it wouldn't make me shit my pants immediatly, because of how almost funny that part was to me(maybe i'm crazy but that part really did make me not scared of the rest of the movie but instead thrilled about what would happen)
The whole thing was just released in a way that was very beginner friendly in the horror movie genre, and I haven't really seen a movie get released after the soundtrack is out. It gives you a good sense of what to expect in the movie while still being distinctly different than the game. And that was so nice to be able to prepare for scary movie number 1.
idk i have a lot of thoughts about it and it was really nice of mark to do those things for a new audience of horror watchers whether it was intentional or not because it did help ease nerves about watching horror movies for many of the people I know.