The "bunker" mentality goes back to Rutherford. As a kid in the '60s, I remember public talks about preparing to go "underground" during "persecution and the use of reversible coats. In one talk, a school friend demonstrated his reversible coat and foldable hat on the stage during the hour talk by an Elder.
Bethel had more tunnels than a rabbit family in the 70s.
And of course, we can't forget GB 2.0's bunker fantasy.