Prior to captaining his first Mosconi Cup (2006), Johann was the head of the Royal Dutch Billiards Association acting as both instructor and coach to a number of top pool players. But more importantly, he had tremendous credibility with MC players such as Niels Feijen, NVB, and Alex Lely.
And, IMO, that is the key ingredient for a successful coach - credibility. Without credibility, it is difficult if not impossible for him/her to motivate, teach, or lead any group to success.
How do you gain credibility? For this, there isn't just one path. Sometimes, credibility is earned through past coaching success (Johann, Bill Belichick, Marv Levy, ...). Other times it comes through past playing success (Ray Reardon, Lenny Wilkens, Joe Torre, etc...).
But all great coaches, BEFORE given the opportunity to prove their greatness FIRST had to be credible.
Mark Wilson has a sh*t ton of credibility, yet he has been unsuccessful. Your point?