I'm guessing the Emerald City is based on that city from the trailers where Sonic chases the armoured police fan. Doesn't look like the Oz kind of city though.
If it has the same name with the city in L. Frank Baum's Wizard of Oz book (which was my favorite book when I was still in school, that and Around the World in 80 days), it's probably coincidental, since Sonic universe love to use the world Emerald : Emerald Hill, Emerald Coast, Emerald Town.
Candy Crush is still a thing? I thought the Emoji Movie killed what was left of it.
I doubt the Candy Crush players watched or even interested in that movie.