Do you have the slightest idea how many variables to check for correlations there are in a biological system as complex as the human body? And how few of those variables can be reliably measured and analyzed at the same time in most of these studies?
Yeah I know, I used to work for a single-cell molecular neurobiology group. But you're citing a development that mostly took of in the last decade, and your question was "why wasn't this already a well known fact?"
That implies disdain that this wasn't discovered ages ago, to the point where it is widely a known truth among regular people. A fact discovered relatively recently as part of very exciting new things that are taking place in biology and medicine would not qualify for that.
