Anyone who thinks that Amazon won't have to implement similar anti-copyright protection is delusional.
Amazon has a bit more leverage against game publishers than Google, I'd imagine. I don't think they're likely to use it in this manner, but it's there.
This assumes that it's game publishers where there's a copyright problem, which given the recent Twitch muting of copyrighted audio, is probably not the issue that most people are concerned about right now.
Right. As a stark difference from the music publishers, the game publishers want people to stream their games.
Why? Whats the difference?
ContentID, versus a company not knee deep in the consumer video industry.
While Amazon may not have a YouTube competitor, they certainly have a consumer video product in Amazon Prime Video.
Twitch already rolled out their own ContentID-styled system, pre-acquisition.
Pre-acquisition announcement! The timing of the two is so similar I think it's beyond likely that the anti-copyright protection wasn't a part of the negotiations.
Amazon is in the music and video industry. Twitch already has content ID. Amazon is pretty much Google-level evil plus sweatshops.
Amazon sells actual products to consumers, Google sells consumer data to advertisers. That means Amazon tends to be more responsive to end-users.
As an experiment: Compare trying to get somebody from Google support on the phone vs. Amazon.
Something no-one else seems to have mentioned in response to you is avoiding monopolies. Various changes to youtube regularly piss off people uploading content to the platform, so having a competitor (twitch) gives them somewhere to run to, and competition in the video market.