So what if they turn on you? Once you’re rich just admit it’s a scam and walk away. The believers will continue on.
Jehovah’s Witnesses predicted the end of the world in 1914. When that didn’t happen they lost members but came back quickly enough. Then they predicted it for 1975. Same thing happened, and now they have more members than ever.
As a board game hobbyist, that happens all the time. Our community generally makes an effort to direct them to games with a lower weight and easier rules and encourages them to keep playing to grow the hobby.