I think this thread is pretty pointless, as there is no right answer and it's just another thread to further popularize people who are already popular. People are pretty much saying their favorite Youtubers. Let's say you think Blamph is the most influential person. Blamph wouldn't have come to the community if his cousin hadn't showed him Minecraft, so his cousin is technically more influential than Blamph himself. However, MCSG wouldn't have come about at all if it weren't for ChadTheDJ. And we needed team Vareide to build our first three maps.
Further, MCSG probably wouldn't have come about if the movie hadn't come out, so I'd hand it to the movie producer, or Jennifer Lawrence, the star of the show. Of course the movie wouldn't have come out if Suzanne Collins hadn't written the book, but Suzanne Collins needed her mother to be born. And MCSG needed developers to be born. And developers needed their mothers.
Do you see what I'm getting at?
Despite the pointlessness of this thread, I'm gonna say the hardest working developer is the most influential person of MCSG, since he has probably spent the most time doing direct good for our community. And his work has a much larger influence than mere moderating or popularizing. (MCSG would have become very popular even without many of our beloved Youtubers. Most people who watch MCSG on Youtube have already tried the game.)