Joined up thinking ? I think not
Elements of it may be more joined up than you think. The cost of keeping extra infrastructure in use / maintained for the last 30 - 40 years would probably have been higher than the cost of retaining it, and could have meant further significant losses in the past. Some of the cuts (Bradford North Curve) should never have happened others are more understandable and justifiable.
I'll add Taunton, Temple Meads and Chippehham to your list, if I may
Under
BR▸ there were political considerations too. If you remove spare capacity (even if its retention would have been very cheap) you demonstrate to the politcos that you are running a lean network. If the amount of capital tied up in infrastructure fell each year the government were pleased.
In a similar vein, BR made many of its stations "open" (removing the barriers). Even if the increase in ticketless travel made no economic sense (ie the barriers and their staff more than paid for themselves), the open stations made
political sense becasue BR could point to year on year reductions in headcount as evidence of agressive cost cutting.
Now under
NR» , the huge debt of NR is secured (essentially mortgaged) against the value of the infrastructure assets, so the incentive to reduce the value of the infratructure needed to run the railway is reversed.