(Disclosure, I didn't actually watch this video.)
This is the second streamer I've heard of moving from Twitch to YouTube recently. Did something happen at one or the other of those sites?
I watch a lot more on YouTube than I do on Twitch, primarily because I prefer to watch on my own schedule, and it seems like there's a perception that Twitch is for live streams and YouTube is for prerecorded stuff. But there's no reason it has to be like that.