They were, and still very much are, using web components. But they hired a team to do experiments to imagine the future of GitHub UI, and that team built everything in React. Now that team's work is being ported to the production UI.
Genuinely whoever was a part of pushing this rewrite should have been fired.
I guess what I’m really saying is that the internet would be a better place if you and others like you dialed down the rhetoric, dialed down the outrage, and dialed up the empathy.
Thanks for listening.