> A truck and a tank have a lot in common

Maybe in 1942. Modern tanks cannot be built on highly specialized production lines that build road vehicles without years-long re-tooling. M1 Abrams tanks don't even use piston engines, they have turbines.

A older, but well documented example how specialized modern automotive production has become is the Mercedes Benz 500e. In the 90s Mercedes wanted to build a more powerful, wider version of the E class. They added 56 mm to the front fenders and discovered it wouldn't fit through the production line properly. MB contracted for Porsche to handle the low-volume 500e on a different production line.

if we need tanks we need people who can build assembly lines. Retooling existing lines isn't the only option.