Back in the mid-late 1990's.
The Freddy Franz era really hammered it in to the heads of the JW's that the ''king of the North'' was none other than the Soviet Union. Then the Soviets suddenly collapsed in 1991-92.
& then
The 1995 generation change, in the Nov 1995 Watchtower. The whole understanding of the 1914 generation evaporating in one WT.
With those 2 fundamental teachings blown away with mere years of each other, well you put 2 and 2 together,... it no longer adds-up.