What is the main qualification to be on the GB?
That you won't rock the boat.
So they choose people who have followed what they say without hiccup for many years.
Like all bodies of elders there are the alphas and the betas. As long as you don't have two alphas fighting each other then they just choose yes men into the group.
From what I see they all like relative power and they all toed the line to the man above them in the pecking order. You don't get to D.O. or branch committee member without that.
But most of all they had to take the wine and crackers without raising suspicion.