I will note that the basic rationale was the time-honored notion that "two heads are better than one." I completed residencies in both internal medicine, and preventive medicine/public health. That's a pretty expansive domain already. The idea of maintaining any semblance of expertise in those disciplines, and adding the full expanse of natural medicine (i.e., botanical and herbal medicine; mind-body medicine; traditional medical practices; acupuncture; massage therapy; etc.) seemed rather far-fetched to me.
So instead, when the opportunity came along to establish an integrative medicine clinic for reasons I've addressed before, I went looking for the well-filled head with which my own might collaborate. Naturopaths were the obvious choice.