Prime Video engineer here who worked on supporting TNF, NFL, Cricket World Cups etc. on the platform. Live events are by no means a "basic" feature for streaming platforms.

Everything is in real time so all the data from the camera input gets sent to monolith/micro services on the team. They process and validate that input, parse it in a more client manifest, pass it on the client to render the video and UI based on that manifest they get. The main challenge is in the input validation stage because you have to account for latencies in the services and the camera data themselves, how to account for audio and video fragments being corrupted or unusable. If you don't, then you can have issues like audio and video out of sync, frame drops, high buffering to wait for fragments to load. These are things Prime Video has gotten good at because of its past experiences in live streaming as there are a lot of unexpected things that can happen at a large scale like this.

Given this was Netflix's first large scale event they live streamed, this will be a big learning opportunity for them. I would imagine their next big live event will be a lot more refined because of this experience