In fact python had general coroutines first in yield, which is mostly used for iteration (“generators”) and state machines.
Some frameworks (e.g. twisted) did use them for concurrency, and the core team originally planned something similar, however the ergonomics were not what they wanted (especially when mixing coroutines-for-concurrency and coroutines-for-iteration), so they went for a more specialised design.
Kinda? But that was a very short cycle, both promises and generators were added to the language in ES6 (though the community had been coalescing around promises — “thenables” — for a while), the first draft for async functions was actually created during the development cycle of ES6, and it was shipped in ES7.
Some frameworks (e.g. twisted) did use them for concurrency, and the core team originally planned something similar, however the ergonomics were not what they wanted (especially when mixing coroutines-for-concurrency and coroutines-for-iteration), so they went for a more specialised design.