The whole AirPower saga is a weird event in product development. AirPower compatibility was highlighted as a feature in the packaging of the just-released AirPods 2 : https://twitter.com/itsnicolenguyen/status/11106569269650636... There has to be something that caused this abrupt cancellation.
I'm imagining some engineering teem at Apple telling their bosses "yeah, it's almost ready" and the bosses believing them without really caring, because it's just a silly accessory and no big deal, right? And then since the AirPods 2 announcemen, the internet has been rabid with anticipation for AirPower. announcing it is cancelled is a better PR move than letting that internet fanboy frenzy turn into frustration with delays.
I wouldn't be surprised if we see AirPower turn up again in a years time.