Erlang also enjoys quite a lot of optimizations on the VM level. E.g. a task is parked/hybernated if there's no work for it to perform (e.g. it's waiting for a message), the switch between tasks is extremely lightweight, VM internals are re-entrant, employ CPU-cache-friendly data structures, garbage collection is both lightweight and per-thread/task etc.

Javascript's async/await probably started as a sugar for callbacks (since JS is single-threaded). Many others definitely have that as sugar for whatever threading implementation they have. In C# it's sugar on top of the whole mechanism of structured concurrency.

But I'm mostly talking out of my ass here, since I don't know much about this topic, so everything above is hardly a step above speculation.