I think the point of it being presented at I/O was a new API that lets Youtube streamers sync up the "superchats" with anything they want in the real world.
Why didn't Twitter make this money a long time ago? All those tweets scrolling across TV for free...
Because Twitter can't deliver any kind of new product.
Because tweets are mostly curated for TV audiences. Paying for top tweets would show that editorial staff doesn't give a flying fudge about their audiance, and simply want to make money (which you are also giving it to them by sitting through commercials).