I'm somewhat surprised that the article's list of conjectures didn't include one: that Italian Parsley may have just been viewed as superior for all use cases (which IMHO it kinda is, outside of Mexican recipes.)
I feel the opposite: Cilantro is superior in all cases except perhaps Italian food, and even Italian food I am skeptical that Cilantro could be better if not for a bias from tradition.
Parsley tastes so bitter and one-dimensional and you have to remove the leaves from the stem, whereas Cilantro is aromatic, fresh, and you can eat the stems making it trivial to prepare. I even go so far as to substitute cilantro for leafy greens in salad.
That's a pretty bonkers statement. Cilantro is much more used worldwide (by about an order of magnitude). They look very similar, but don't taste anything alike. You might as well say basil is better than oregano. It's just not a very meaningful statement.
In a lot of the world flavor is about stacking complex flavors to get a melange of them. With the establishment of the top end of European cooking as French haute cuisine, there was instead an emphasis on simple, clear flavors. In that style, parsley, as a much more subtle herb, shines.
I didn't say they had the same taste (though they're way closer than basil and oregano.) The question is whether the ancient Cilantro recipes that the article posits became Italian Parsley recipes.
Subtlety gets evened out by different preparation techniques. IMHO, when used raw, finely chopped Italian Parsley is at least as intense as coarsely chopped Cilantro.
