The Bulleid pacifics were rebuilt from chain drive to Walscahaerts at great cost, the calculations were said to have been amortised of a service life to end in the 1980's
That is a clue, The rate of change of tramsport technology must have been very under-estimated,
The Railway finances went put of control in the early 60s, hence Dr Beeching!
BR abandoned steam, branch lines, coaches and wagons at great rate, in order to contain costs.
I hear the same underestimation of changes in technolgy with the much heralded driverless car.
The driverless car is only being held back by a few shortcomings, one being the cost of the Lidar laser imaging device, when the Lidar cost falls theh driverless car will arrive on our roads very quickly
Didn't NBL Co fall over, mostly because they expected steam construction to be phased out over around 25 years and that was even after British Railways had announced the end of building steam. They expected the Empire to slowly follow suit, but the foreign railways, wanted to reduce their costs too! So instead of a long lead time, construction of steam stopped, almost overnight.
Yes the driverless car, isn't far off, with lots of trials.