The original idea was the classmates sending Momo with Hiems because they doubted he'd be caring enough. Butnow that he has candies from a questionable source the myth has been busted.
It's a bit late, but should there be Christmas doodles for our wonderful Nensu and Midoriya ship? don't ask about Hiems and Momo, it'll probably be her complaining about Hiems trying to skip breakfast for extra sleep