They did claim they have ppl DMCAing streams of the event, and Twitch did take some of them down for copyright. So, the excuse is still bullshit ,especially since under their own TOS, if you notify them what the copyright material is so they can identify it, they will take it down as they do identify it. Specifically point 3 says “Identification of the material that is claimed to be infringing or to be the subject of infringing activity and that is to be removed or access to which is to be disabled, and information reasonably sufficient to permit Twitch to locate the material. Providing a broadcaster’s feed and the time on such feed at which you believe there has been an infringement is the best way to help us locate content quickly.”
That means, you don’t even need to provide a stream, it just helps them find it faster. So, if they got a DMCA for one stream, it makes no sense how so many, especially with the amount of viewers, got to stay up. If they don’t wanna do anything, who really cares, but that excuse is so shit, especially based on their own TOS.