It is true that on Twitch, when a popular game has drops, the viewer numbers go through the roof. But I don't think you can extrapolate that an unpopular platform could pull viewers away from Twitch by having a bunch of unpopular streamers do drops. You'd probably influence which streamers on Mixer got viewers on Mixer, but would it get people to drop Twitch? I strongly doubt it.

More to the point, no other platform has succeeded here either. Whatever that Facebook streaming thing is is a non-factor, YouTube streams exist but seem to be used primarily as a way for YouTubers to do events rather than a real Twitch competitor, etc. I'm not sure a Twitch competitor can be viable until Twitch does something to drive people away. The network effect is strong.