They’ve tried that. The rail fragmentation enabled dozens of companies to take on specific lines.
It failed.
Compare and contrast to British Telecom. They converted the state monolith into a private monopoly. BT operated for years without competition, services improved... But the advent of fibre broadband has flooded the market with competition forcing BT to up its game.
From 3 years ago...
There must have been no incentives to succeed
Giving it to one or many is the same thing if there is no incentives to succeed and no consequences for failure