An elf suddenly stumbled out of the workshop and collapsed in the snow. Santa ran up and found a knife in his back, with a note attached to it. He read it: "Dear Santa, we're tired of Christmas being the most over-used holiday of all time.So we've teamed up to kill it, you, and anyone who stands in our way." Santa wasn't about to let them kill Christmas without a fight. He gathered up anyone who wanted to save it. Shit was about to go down.
I'd say they're jealous and stuff, so they wanna kill the Christmas-guys and become the new most anticipated & loved holiday. Something along those lines.