Probably for the holidays.
>this friendly, fat Santa in these bright red robes, which, I don't think is a coincidence, match the color of the Coke logo — this really took hold in American culture."
http://www.npr.org/2016/12/20/506215632/how-red-and-green-be...
The question may even be referring to the rationale of having HN decorated for Christmas at all, given that it's not universally observed.
Given where HN is based, and that the holiday is fairly well known even among those that don't celebrate it, I assumed it was obvious - my mistake.
