There's a general principle of prior use as an absolute defence in trademark law - though it wouldn't surprise me to much to find that USA had violated that principle.

Candy is too generic in both the software field and the game field to be a distinctive mark and so shouldn't be granted as a word mark; trademark examiner fail. I mean come on.

http://www.girlgames.com/kittys-candies.html from 2011.

http://www.primarygames.com/puzzles/strategy/candybags/ from 2008.

http://www.cookinggames.com/minas-popping-candies.html from 2011; almost an exact match for Candy Crush from King.com Limited.

"Candy" thus would confuse people as to the origin because of this lack of distinctiveness and widespread prior use in games and in apps.

The dates for these prior uses are from Google and hence can't be relied on but better dates could be acquired. This search took 5 minutes at most.