Randy reports in his linked article about the apostasy back in the late 70’s but there were several causes: Nothing happened in 1975 and people were looking for other interpretations of prophecy, change of leadership because Knorr was dying and this resulted in loss of unity when the leader was demising, people back then in that era also had that tendency to interpret the Bible on their own.
In 1976, they changed the 4 year Bethel rule to 1 year and a lot of people that were expecting 1975 left including couples and others that were there a long time, and disgruntled who could not leave before 4 years. Some who stayed —except the newboys who didn’t think about leadership or doctrine— got involved in personal interpretations of the Bible and Schroder strongly felt it was influencing the thinking of JW. Schroder came down hard on that because he felt it was confusing the faith of JW. They wanted to put a stop to it.
People get angry and offended an hurt and believe their position is right and they leave or they get kicked out. but the 2 main reasons is 1975 and Knorr loss of power.
NYC streets were perilous back then. Car breakins, muggings, armed robbery were the common place. But inside wt complex you lived in a different world. That was your reality.