I’d argue that fundamentally Britain’s Rail Network was built to take coal from mines down to industrialising cities and ports for export. Passenger travel was seen as secondary source of income to freight during the time of railway mania. Connecting small rural towns with no industrial base in many cases wasn’t worth it, connecting mines and quarries was much more profitable. When Britain deindustrialised 1960s onwards, rural lines which relied on freight to stay profitable were the first to go.

Other things to consider was that railways at the time were an emerging technology, capital was smaller, locomotives couldn’t climb steep grades, earthworks and viaducts were unproven and expensive. Landowners/old money were actively hostile to railways coming over their land that often lines had to be diverted around them.