Bryan Cantrill's talk about Rust addresses when they removed green threads, and how much of a bold, disruptive change that was. He remarks on how that impressed him with the Rust community and made him follow the language more closely - had they been too scared to change the language in drastic ways, we would still be stuck with green threads.

Sorry, I can't remember the timestamp right now but the entire thing is worth a listen:

https://www.youtube.com/watch?v=LjFM8vw3pbU