An exact reason for the layoffs was not explicitly stated, but it could be that Telltale became a little too large for its own good, with around 400 employees (before today) and a number of licensed projects like Batman, Guardians of the Galaxy, Game of Thrones, etc.
I didn't know their staff was as large as "around 400" people.
Not surprising they have to "downsize," but I feel bad for those employees who lost their jobs for Christmas.
I've seen a lot about this on Twitter... though I'm not a great fan of their games since they started away from more traditional point and click adventure games, I hope this works out both for Telltale and that those laid off can find new employment soon.
Whichever way you look at it and whatever the exact reasons are, it's sad news. :(