TTC vs Xio involved a direct clone. The judge ruled in his ruling that the game rules and gameplay were not copyrightable. Indeed, the judge noted that games like Dr. Mario (a tetris-like) would not have violated TTC's copyright.

Xio's clone went beyond just rules and gameplay--it copied the dimensions, colors, and various art assets. Comparing screenshots of Tetris and Xio's clone, it would have been very difficult for most people, even those familiar with Tetris, to identify which was the original.

Xio’s game didn’t copy any art assets from anywhere, as I can tell you, since I made all the art for it. [Mostly over one weekend, as a volunteer favor to the developers.]

The colors were not copied from anywhere, they were picked, by me, with no reference to any existing art, using a careful process designed to maximize distinguishability. To be specific, I decided that the colors should all be clearly separated in CIELAB lightness and hue, and then chose which lightness to match to which hue based on the gamut of then-current iPhones.

The result is a bunch of “bright” colors. But lots of games want bright colors, because they are the most easily distinguishable, and having easily distinguishable colors makes a game easier to play.

As for the appearance of the bricks, I cooked up a dozen or so possibilities in Photoshop, and let the rest of the team decide which to use. Again, created in a few various styles, but not with any reference to any previous game.

Just look at the screenshots of Xio's clone and Tetris. They are almost identical. Now compare Tetris with tetris-likes such as Dr. Mario, and the difference is immediately apparent.

Copying assets doesn't just mean verbatim copy-and-paste. It includes recreating other assets such that they are virtually identical to the source material, as the art assets you apparently created were.

IANAL, but these are two different issues. We are discussing a trademark, not a mechanic. TTC never got any of their cases regarding trademark, precisely because no one called it tetris (which is not even a real word). King hasn't copyrighted match-3, and probably won't ever be able to (what with prior art with at least Bejeweled, and I'm sure others before that)

Even aside from all that, I think #candyjam is protected under fair use. The intent is very obviously parody. In fact, it'll probably end up with someone participating in the jam that has a sizable legal team, and they could probably string up a class-action lawsuit for everyone in the jam, which would probably amount to huge settlement costs if King tried to pay their way out of court. Lose-lose situation for them; they shell out massive amounts or lose their trademark for not protecting it.