People have been doing collaborative text editing since the 60s actually! See, The Mother Of All Demos[0], referenced in our first blog post[1] :D

I'd say CRDTs are also a big change. CRDTs make live collaboration much more robust for all parties involved, and they only started to reach maturity in the mid-late 2010s

[0] https://en.wikipedia.org/wiki/The_Mother_of_All_Demos

[1] https://zed.dev/blog/crdts