As we're still a ways off from Bethesda releasing a new mainline Fallout game, modders have taken it upon themselves to make ambitious projects that keep the universe alive and interesting. Fallout: London springs to mind, and Fallout: Vault 13 was a similar project.
Beginning work in 2021, Fallout: Vault 13 was a mod that sought to remake the original Fallout game using Fallout 4's engine. It released a demo and a lot of work had been done on it, but according to a social media post from the mod team's leader (via Eurogamer), the scale of the project simply proved to be too much.
"After much careful thought and deliberation, we have decided to officially suspend development on Fallout: Vault 13," wrote project founder and co-lead Culinwino. "This was not an easy decision, but we believe it is the right step at this stage of our journey."
As the team was made up of volunteers, burnout proved to be the killer of the project. There was no infighting nor did Bethesda come along with a big cease-and-desist sized hammer. There is still a spark of hope left for the project, as the demo is still available to download and the current build of the mod is set to go up on the Nexus. Perhaps someone else will pick up the torch.