What are some examples of people working alone on a project for 10+ years?

What a delectable rabbit hole! My favorite from that thread probably Dwarf Fortress - a game that uses text symbols for graphics to create an enitre fantasy world. This article from 2013 talks about how Notch drew inspiration for minecraft from it.

https://www.wired.com/2013/11/minecraft-book/

There is something special about seeing someone commit an inordinate amount of time to singular focus. Following that thread to see who/what else follows...who inherits the obsession and how they evolve it...I could read all day about it.