Linux is certainly large enough to outlive Linus.
TempleOS continues to live.
Dwarf fortress might not be maintainable by others if the worst were to happen, but there is a very dedicated community.
Are there any examples of the bus factor actually ending a project?
If you have a group of developers with a common vision and time and users who find the work useful then the project might continue.
Can’t think of examples of such a project ending though.
Examples where a community successfully turned the ship around, are Rust, C++ and PHP. But there it were not the community, it were the companies behind driving improvements.