How did the world of the Mortal Engines, in the aftermath of the Sixty Minute War, manage to do something we can't do today?

Question

In Mortal Engines, the Sixty Minute War devastated civilisation as we know it, leaving most 'old tech' completely inoperational. Yet, despite the collapse of technology as we know it, they managed to do something that literally could not be done today: put cities (most astonishingly, London!) on giant traction treads.

In other words, the paradox is:

Today: Lots of resources and tech. Literally could not do traction cities if we tried.

Traction Era: Minimal resources and tech. Has traction cities.

Is there an in-universe* explanation for this?

*(The out of universe explanation is obviously rule-of-cool)

Answer 1

"Necessity is the mother of invention" combined with the fact that the 60 Minute War probably starts 1500 or more years in our future. Given our current rate of technological advancement we can only guess what another millennium and change will bring. I'd also argue we do have the materials and engineering technology to build something like a traction city in the modern world. We couldn't get something like that to move, let alone do so at speed, but we could build it given enough money, materials, and motivation (of which we have none whatsoever).