Pakistan Railways has been depreciated? Why? Is this a conscious policy?

Railway system was one of Pakistan's major assets 40 years ago. BBC mentioned it as one the great Railways of the world. 

The system has now been depreciated to almost a standstill. 

Why have we depreciated such a major asset? Was it a conscious policy? Or just ignorance and poor management?

How can railway be fixed? 

Should it be fixed? 

This is an overview discussion to be followed up by others on this topic