Twitch "permanently" won by injecting ads directly on the feed, right now best you can do is sneak swap the small resolution version that stay on the side until they also removed this.
Actually the modern vaft script can completely bypass ads and has seen minimal changes for well over a year. Twitch gave up because most people, even the tech savvy ones, don't know about the solutions anymore.
There’s no need at all to rely on Chrome: If Google wanted to, they could enable DRM for all videos on Youtube today. Almost every desktop and mobile browser supports it.
They’d lose a couple of legacy client apps, but much less traffic than they would if they were to make it Chrome-only.
They could always exempt Youtube Shorts (which are competing with TikTok/Instagram reels etc.) from DRM and only apply it to longer-form content. Shorts don't get ads anyway in my experience (but I almost never use them).
In the sense that Google pays for search engine placement, yes. They also pay Apple for the same thing - I'd hesitate to say that gives them much influence over either Firefox or Safari.
Until Google changes how the web works and all other browsers will align. And they can do that, since they almost own the web trough Chrome.