I read an interesting report about high speed rail development in Europe. It was comparing Spain and UK a lot. Spain has the biggest high speed network in Europe (second biggest in the world after China) and UK failed to build a single line after the costs reached $100B and project was scaled down. Spain is also building its network at lowest cost in Europe. According to the report the main reasons for that are:

• consistent political backing: all parties support rail development so over the last couple of decades the entire process was optimized
• consistent support on all levels of administration: central and local governments support rail so the plans don't change all the time. proper planning can be done
• mature public-private cooperation: over the years government and private companies learned to work together to build quickly and cheaply while maintaining quality

What is happening in UK and USA is that high speed rail is a for-profit project for private companies. Government promises them $20B and they start building. If they finish the money dries up so they never finish. When they spend everything government gives them more money. They can't cancel the project because thousands of people work on it so they just limit the scope making it less and less useful. In the end the rail doesn't even reach the cities it was supposed to, less people can use it, everything stops being economically viable and the whole thing collapses.

Basically in Spain private companies make profit as long as building railways makes economical sense. In US/UK they make money for as long as government can fund them. Building anything is not the goal.