Through his son Michael, Sonny Franzese supervised a gasoline-tax-evasion scam that turned into a billion-dollar enterprise lasting for six years, until the FBI broke it up in the mideighties.
As I understand, the clause "that turned into a billion-dollar enterprise lasting for six years" modifies "a gasoline-tax-evasion scam". What confuses me is how a gasoline-tax-evasion scam can turn into a billion-dollar enterprise lasting for six years. It doesn't seem to make much sense. Any thoughts on it?
Edit: To clarify my question: I know "turn into" can mean 'become', but I feel a scam becomes a billion-dollar enterprise is a bit strange.