thisIsNotMe: I'm confused by this. There is NO process. They pick whoever they think fits best and that's it.
That has always been the way the GB/F&DS operates. Russell, Rutherford, Knorr... all well known for shaping the organization as they pleased. Heck, Rutherford took control literally over Russell's dead body.
The selection of relatively young men is a sign that they're prepared to be in for the long haul. For all the talk about how close the end is, the older GB members know that they'll pass away in the 'present system of things' and will not see an event that isn't ever destined to happen. They're leaning into the grift. Someone has to manage Ramapo, after all...