Some streams have nothing to do with the game but more about the person who plays them. Some people are attached to the streamer and their personally, the show, his comments or knowledge. vCOH or COH2 had nothing to do with the 3.5k viewers in this case.
Another example is this guy:
http://www.twitch.tv/dansgaming
No mater what game he plays, he will get 5 to 10k viewers
EDIT:
While looking through his highlights, I thought this was pretty funny:
[twitch=dansgaming]chapter_id=4440374[/twitch]
What a fool...