The hardest thing was mapping approximate date descriptions (think "1st half of 17th century") into years to draw on chart.
I've once built something similar for myself (still at https://github.com/fdw/timelines/), but not half as polished as yours. I like yours better ;)
I wonder if you took inspiration from "The Timetables of History" (https://openlibrary.org/books/OL1756160M/The_timetables_of_h...)?
That book has always been a favorite of mine to just meander through and find interesting parallelism, but incorporating Wikipedia links as you've done adds a new dimension.
https://github.com/SeanHollen/1300-2000
I like how your project has such a long time horizon, I'm glad you're showing it.
Another project in a similar vein that might influence you is the historical tech tree. https://www.historicaltechtree.com/ It has literally thousands of technologies all mapped together. I was curious so I calculated the most "influential" technologies: https://github.com/etiennefd/hhr-tech-tree/issues/12
I'll also have a look around your repo. And maybe I know feel inspired to put some more work into mine - thanks for the kind words.