Why build and maintain the entirety of the infrastructure for a national transport system: payment, timetables, rails, signalling etc. and then hand the very last bit - the only bit that actually generates revenue - to a private company?

It's just another example of the hubris of the Conservative party. We've seen it play out repeatedly over the last decade and even earlier in Thatcher's neoliberalism. Labour's lurch to the right resulted in displays of similar small minded arrogance. Their undermining of the NHS through piecemeal privatisation is nothing short of a crime.