[pm90]

Well, its all relative.

Today's technology makes it easier to analyze and discover causative agents very easily for such issues (consider how quickly we were able to identify, sequence the current coronavirus... a virus!). The harder problems lie at the edge of where our current instrumentation is able to take us.

In the article, it took several years to identify the agent that prevented blood clots, today it would take days. But there are other things that take as long because we don't yet have the technology yet.

So at every stage in humanity, the "low hanging fruits" are so only in retrospect. For the people in 1920's, this problem was definitely not low hanging : )