Authorship typically goes to the director, in this case James Mangold. The article did mention him.
What an odd response. Presumably the grandparent post meant the author of the article, which is omitted (as far as I can tell).
The grandparent specifically wanted to know who the authored the propaganda. The article is just about box office scores. It's not something a sane person would regard as propaganda. Hollywood movies however have long served as a core component of American soft power.