Maybe it was his background studying and teaching science at the University of Arizona. That discipline admits there are no absolute answers, only theories which seem to hold water, at least at the time. Or perhaps the humility he displayed during the panel discussion resulted from his struggle with his own physical problems.
Whatever the source of his low-key approach to the issue of the power of prayer, it was what drew the lion's share of attention from us in the audience - before, during, and after the presentations. In itself, that humility was a kind of charisma.
The takeaway here could well be: Leave space around your topic so that those in the audience have the cognitive, emotional and spiritual room to play around with the content. Don't push expertise. Don't demand allegiance to a point of view.
The New Humility is the New Cool.