Complex sentence: Expanding railway networks (in the US and the UK) fostered a demand for steam shovels; it can be said that the extensive mileage of railways, and corresponding volume of material to be moved, forced the technological leap.
Split into simpler sentences: Expanding railway networks (in the US and the UK) fostered a demand for steam shovels. The extensive mileage of railways, and corresponding volume of material to be moved, forced the technological leap.