When I first bought a PC one of the first things I did was mod Fallout 3 until it crashed. The mod in the image is called Acquired Immunity and I assume I downloaded it when I was looking for perk mods such as Ultimate Perk Pack. Essentially instead of siding with either faction in The Pitt DLC it allowed you to eat the baby who has an immunity to radiation to get the immunity yourself. Considering how dark the Fallout series can be at times (ex. Meat of the Champions perk in Fallout New Vegas) and how it was implemented I didn’t really question it too much.
I’ve also experienced something similar with full dialogue mods for Fallout 4.
I also wanted to mention there’s a Fallout community on Lemmy if you are interested.
I was wondering what mods did you assume were part of the base-game?
I’ve had the opposite happen to me. I thought that the entire story of Starbound was a mod because the only time I played it unmodded was before they completely overhauled the story.