Amazon had their fair share of livestream failures and for notably less viewers. I don't think they deserve a spot on that list. I briefly worked in streaming media for sports and while it's not a novel problem, there are so many moving parts and points of failure that it can easily all go badly.
There is no one "Amazon" here, there are at least 3:
* Twitch: Essentially invented live streaming. Fantastic.
* Amazon Interactive Video Service [0]: Essentially "Twitch As A Service", built by Twitch engineers. Fantastic.
* Prime Video. Same exact situation as Netflix: original expertise is all in static content. Lots of growing pains with live video and poor reports. But they've figured it out: now there are regular live streams (NHL and NFL), and other channel providers do live streaming on Prime Video as a distribution platform.
Doesn't twitch almost fall over (other non-massive streams impacted) when anyone gets close to 4-5m concurrent viewers? I remember last time it happened everything started falling over, even for smaller streams. Even if Netflix struggled with the event, streaming other content worked just fine for me.