alt Hacker NewsThe point is that Japan has a well-established private-equity industry [1] so the fact that PE firms haven't ruined Japanese railways suggests that PE firms aren't universal corrosive solvents like you seem to want us to believe they are.
[1] https://flippa.com/blog/pe-funds/japan-private-equity-firms/
Or it could be there are Japanese laws or customs preventing them from doing it. The article mentions maximum fare prices for example. Japanese antitrust law is strong and thoroughly enforced.