> More recently I'm still not sure why, in a language with an extensive runtime and its own VM, they went with async / await rather than fibers or continuations

> More recently I'm still not sure why, in a language with an extensive runtime and its own VM, they went with async / await rather than fibers or continuations like go and java. It was probably simpler to implement initially, of course. No one was willing to approve another extension of the old runtime, and a major one at that. If they had already completed the .Net Core rewrite back then they would've probably baked async into the runtime.