That is an interesting question. I think it’s because when a researcher/doctor decides to prove a theory they look to prove or disprove it before anything else. Clearly IL-6 targeting has some effect. Most likely they never bothered to look deeper because they’d proved their theory. (This is a broad assumption but I do think it mostly applies)

Here’s an example of that sort of narrow focus from my personal life...

My father had a bad back. Disc problems. Had to take a lot of pain meds at times just to be able to do the one thing he loved most, golfing. He decided, a couple of years ago, to finally get surgery. In October of that year, after lots of appointments, x-rays, and tests they got him under the knife for a discectomy and some other major thing in his lower back. By February it seemed the good results were getting worse again and by May he was dead of the stage 4 intestinal cancer that had spread unnoticed throughout his stomach the whole time. How nobody noticed he had significant cancer through all the poking and prodding and x-rays is a really tough thing for me to reckon with. Seems impossible. But they were zeroing in on his discs and not bothering to look at anything else. I don’t think they did anything wrong. They did a great job of diagnosing and fixing his back problems. But similar to how they are trained to look at a patient’s symptoms and draw the most obvious conclusion (working down from there) before ever drawing the more obscure conclusion, I can see this kind of missed opportunity playing out in research all the time since the body is so complex.