I agree the idea of this place and others like it are unlikely to have been built merely for shelter from invasion. A more cataclysmic scenario is where my mind has been going since I first learned of the site. It's interesting you mention a tunnel network that crossed from Europe into Turkey as I've heard snippets of that however not really dug into it. Something profound occurred to inspire people to go underground in such numbers, but what?
With each investigation into these ancient sites I come out with more questions than answers. Frustrating but fascinating. Thanks for reading and commenting dude.