Having personally known and worked around half the GB in the 70s, having read the bios of GB 2.0, and having known a few Watchtower Attornies, I would say it is a combination.
GB 1.0 (except Franz and Knorr) were like your sincere average Elders. You could disagree with them(as long as you had a smile) and reason with them. They had "street cred" but no education and average IQs.
The Watchtower Attornies and Accountants have usually been well read experienced elders, WITH above-average IQs, and advanced College Degrees. They are experienced in INFLUENCEING others. They don't claim to have a special "calling"...they don't hear God talking to them. :)
GB 2.0-3.0 have unusual biographies. Long after the official heavenly calling cut-off date they "HEARD" a calling and started partaking. Personally, I think many suffer from psychosis, schizophrenia, bipolar disorder, schizoaffective disorder, or severe depression. IE: "TRUE BELIVERS".
I think the educated professionals have their hands full influencing these fanatical nut cases....therefore the flip flops.