It is one of the best known religious images in the world.
It certainly is a major part of Mexican culture.
Everyone knows the story in Mexico, even if they aren’t catholic.
Maybe you wouldn’t have known, but if you were SOS and had a competent staff who planned your itinerary - don’t you think someone should have pointed out this centuries old story behind this famous image?
I cannot imagine just walking in there with no background knowledge of what I was about to see!
This was not a tough one. Asking who painted Mary of Guadalupe is like asking who painted the Shroud of Turin. You may not believe in the artifact yourself, but the question is deeply offensive to anybody who does.