Why was professor Moriarty free and could not arrested by the police

Moriarty has a great deal of money from his proceeds in crime. They speculate about the man’s illegal activities that procured his great wealth. Holmes knows a lot about Moriarty: he has many bank accounts, and must have extravagant wealth to be able to pay, for example, his chief of staff six thousand a year.

moriarty is free and could not arrested by the police because he never left any clue