Although the Book Study "arrangement" (aaarrrgh! Those words!) finished a few months after I quit meetings entirely, it still greatly surprised me. It was the meeting I was most likely to attend, though overall in our congregation it was the meeting that was least supported.
It reminds me of the old Cold War-era obsession with "Kremlin-watching", in which diplomats and news media used to interpret the statements and actions of the USSR: the Russians would do something and offer an explanation, but the experts knew the real reason was something else, so their job was to figure out the true purpose of a decision made in Moscow. Likewise the WTBTS: as a member you came to know that their explanations for decisions usually shielded the real reason. It was standard practice in congregations for people to speculate (quietly) on the real motivation. It was no real surprise when it turned out that the organisation had sided with Jimmy Swaggart's evangelical holy-roller group in a court battle over taxation around the time they stopped selling their books and magazines in 1990. Yet they never, ever, ever came out and said so in their magazines. That's quite a condemnation of an organisation that is supposedly open and Christian and in which everyone ie equal.
The choices offered in the opening post are intriguing. It struck me at the time that after so many years of poor attendance, the meetings were simply abandoned as an admission that they were flogging a dead horse and that elders were putting in extra effort for no real gain. But it is so out of character for the WTS to simply give up. I don't know any other arrangement they have that they've just abandoned because of lack of interest; I mean, what next, scrap field service?
They would know that very few people would actually have a Family Worship Night, so effectively they are just handing back free time to the brothers, which carries an enormous risk that without repeated indoctrination, more will just drift away.
Maybe the real answer comes down to the adage that given the choice between a conspiracy and a cock-up, such intrigues are almost always a cock-up. In their Bethel Bubble the GB really thought people would embrace Family Worship Night.