But they could establish rules that guarantee transparency.

No regulator in the world has successfully stopped a scam before people lost money (afaik). But if you establish some regulatory framework in which people have to disclose information, establishes capital rules, etc. then it makes that less likely.

Scams are a central component of financial innovation. But this specific kind of scam (stealing money from customers) is basically non-existent at scale today because of regulation.