Sometimes we assume that our academic researchers are narrowly focused and that non-researcher teachers give a broader perspective, but I believe that it can be just the opposite. The top researchers give generalizations based on sampling of populations and/or very general principles. So, for instance, when they generalize about the effects of promotions on subsequent sales, they are not talking about one company or one person's experiences but about the class of companies under study.Click here for the whole thing.
One of my mentors had an amazing breadth of knowledge about pretty much every sub discipline in Finance. I asked him once (over coffee) how he got that way. His response was that as an assistant professor, they made him teach a lot of different classes. Before each new prep (even though they were often undergrad courses) he'd read some of the journal articles in the discipline to make sure he was on proper footing (being a cynic, he often didn't trust the textbooks). So, he'd get an overview of whatever topic he was teachings from a rigorous perspective. Then he could boil it down for his students.
I talk a lot with business people. My experience echoes Danos' comments - most successful businessmen have a deep understanding of their specific circumstances. However, as deep as it is, it's often also very narrow. While a researcher's own interests may also be very focused, the best ones are in the habit of reading a diverse selection of journal articles that are not directly related to their specific topic. This gives them the "broad sample" exposure that makes them good teachers.
Now if only these two guys would post more often.