I watched shroud when he's in Twitch, and when he switched, i just don't bother to even download mixer. I don't think he "killed" his career by moving to mixer tho.
Although i heard his viewers are down compared to twitch, i believe he made the decision to switch from Twitch to Mixer because he got offered something that he can't refuse. He basically got an offer that makes him set for his life. 10 mil for streaming 3 years is a lot of money man. You just have to sit your ass down, play the games you like and not too worried about the income really (although i believe he still earn respectable amount of money in Mixer)
I doubt his popularity changes, its just even he said it, that some people don't even know he's switching to Mixer because Twitch is just the number one streaming platform that everybody knows. But he's still known by that ex-pro C9 player that become a streamer.